Voltaire was definitely considered to be a pest by the French royal court, including him taking a self-exile to Britain, and a short stint in the Bastille.

Will Durant's book "Age of Voltaire", part of his series "The Story Of Civilization", while dated, chronicles Voltaire against the backdrop of pre-revolutionary France, and Europe as a whole.

Voltaire was considered a scoundrel, and a self-made millionaire whose antics infuriated many, but also endeared him to others. He could be pretentious, with his writing being a scathing indictment of what he saw to be flaws in the system, particularly in church.

Now, we look back at him with a different view. A difference maker, a troublemaker with a heart of gold, so to speak. But at the time, he had many enemies over the words that he wrote.

edit: Will, not Charles Durant.

I haven't ever posted in here so I hope it's ok. I've studied philosophy for 6 years; will have a Masters in Rhetoric at the end of December. I don't know much about Nietzsche or Voltaire's person lives, though I know a bit about Ludwig Wittgenstein, who I would consider as a philosopher we respect today. (He studied under Bertrand Russell.)

In a book called Wittgenstein's Poker, author David Edmonds portrays Wittgenstein as somewhat of a introvert with a short temper. My respect for Wittgenstein aside, he seemed to have been one who knew he was at the top of the pecking order and had no problem asserting his power.

In the early 20th century, Cambridge had a prominent intellectual club called the Moral Sciences Club - Students and teachers alike would get together and discuss philosophical topics of interest. Wittgenstein was the chair for a time and the Club invited Karl Popper, another prominent philosopher, to join in on the debate. Mind you, Wittgenstein was known to have legitimate followers, students that would follow him and his studies as if they were truth. Though the details are hearsay and a bit controversial (and much longer of a story), Popper and Wittgenstein got into a heated discussion.

Wittgenstein was known to get very heated during discussions and was known to overtake the room and not necessarily let others speak or explain their line of thinking fully. He allegedly interrupted Popper and began swinging a fire poker around as he was making his points. It was said to have been a method for emphasizing his points. Anyway, Wittgenstein said something about "Name an example of a moral rule," to which Popper said, "Not threatening visiting professors." Wittgenstein then threw the poker down and stormed out.

Wittgenstein was certainly known as someone who made sporadic decisions and didn't maintain very good relationships. Russell even mentioned how Wittgenstein would often fly off the handle during their discussions.

So, long story long, I don't think Wittgenstein had a very good reputation, at least around Cambridge and aside from his loyal followers.

Edit: Granted this is after Wittgenstein published the Tractatus, so he was generally accepted as a legit philosopher at the time of this event.

Going back to Socrates himself, philosophers have often been considered annoying.

Socrates was known as The Gadfly of Athens because he constantly asked questions that undermined the status quo. To this day, the Socratic method of teaching copies his style of questioning the foundation of students' assumptions until a state of internal doubt known as aporia is achieved, in which students become unsure enough of their beliefs to be open to changing their minds.

In Socrates' day, however, he didn't do this with just students. He did it publicly, to professional and popular philosophers, teachers, rhetoricians, and politicians. He eventually pissed off the wrong people, and was put on trial for his life, which he lost.

His argumentative style was ostensibly intended to get his listeners to reach his conclusion of knowledge, that all he knew was that he knew nothing. However, a critical reading of Plato's accounts of his arguments seems to show subtle contridictions that imply this was merely his rhetorical style, and the mytho-philosophical conclusions he proposed after inducing aporia in his challengers were not rational positions, such as his proposition that all knowledge is recollection, and he may have been playing with people's minds just to get them to think. After all, he was the person who first said that an unexamined life was not worth living.

In short, Socrates' style has a lot in common with the arguments of what we would today consider internet trolling.

Sources

The Apology by Plato
Meno by Plato
The Gay Science by Nietzsche, which proposes that Plato's representation of Socrates in The Republic puts forth a false narrative known as The Noble Lie intended not to be truthful, but to protect the weak from the strong via moral and mythological frameworks that form the foundations of civilized society.

Nietzsche scholar here:

Conversations with Nietzsche, edited by Sander L. Gilman is a good place to look as well as Selected Letters of Friedrich Nietzsche edited by Christopher Middleton.

Nietzsche had a small group of friends/followers. For instance, Peter Gast was a close friend of his from their time at the University of Basel together - he would frequently receive correspondence from Nietzsche and help to proofread some of his books and eventually went on to found the Nietzsche Archive with Elizabeth Förster (Nietzsche's nationalist sister). Franz Overbeck also helped in regards to his writings and estate. He was also famously friends with Lou Salomé and the psychologist Paul Ree and also early feminist Ida von Miaskowski. They seem to have recognized his brilliance early on - especially since he was known as a prodigy in classical studies (became professor by the age of 24) - and the myth of the Wagnerian/Schopenhauerian genius was very popular in Weimar circles so they knew that he had some sort of gift.

There are so many great accounts, including Hans von Bülow writing a pretty harsh letter to Nietzsche that one of his piano pieces must be a joke because it was so bad. Also, the letters of insanity are pretty great pieces of evidence how much his friends really cared for and worried about his later decline in health. He also had a couple letters of correspondence between him and August Strindberg that are quite odd so it would seem the outreach of his brilliance had reached Sweden as well.

Basically, people though he was eccentric... because he was... and he wanted to be. To quote Strindberg from one of his own letters to Nietzsche: "I want, I want to be mad!"

Will post more later if anyone wants anything specific though.

To clarify, are you asking simply about how the general public regards philosophers, or how other academics regard philosophers? Because the great philosophers of today are, with rare exceptions, really not known by the public at all, just as many great philosophers weren't known by the general public in their day. Serious academics are often only known by other serious academics until their historical impact has been confirmed (e.g. most people don't know who Saul Kripke is, even though everyone in philosophy does).

As far as how they were regarded by other philosophers, well as many of them introduced great changes in philosophy, they were naturally controversial figures. As such many philosophers considered them wrong, ignorant, arrogant, etc (as many today still consider them. Ask an Aristotelian what he thinks of Hume's knowledge of causality and you will not get a flattering description). Pick any famous philosopher and you will find some other philosopher who thought he was a fool.

It seems however like you're talking about people that we consider fakers, e.g. a teenager who comments on reddit that they can easily refute Kant, or such. If you're wondering whether famous philosophers were considered fakes in their time, I would say not really. Wrong, crazy, overrated, sure, but not fake. And that's also true today. The great philosophers that are currently living and writing have plenty of detractors, but they're still taken seriously. Generally underneath all the vitriol there's still a real respect for their talent. At the very least they aren't thought to be phonies. Take someone like Descartes, who plenty of people thought was wrong, but still was taken very seriously, and compare that with say, Richard Dawkins, who most philosophers, atheist or not, simply don't take seriously (when he speaks about philosophy that is. They might take his influence seriously, but not his thought seriously).

As a side note, I don't think Voltaire is or ever was considered a serious philosopher by philosophers.

That’s a tough question because the popular conception of philosophy is much different than what academic philosophy actually is. There are 2 main schools of philosophy. On the one hand you have ‘continental philosophy’ which is what the public is most familiar with; continental philosophy asks questions like ‘what is the good life?’, and ‘what does it mean to be human?’. On the other hand you have analytical philosophy which tends to be more associated with math. Serious philosophers usually study analytic philosophy, however, because it’s less accessible it doesn’t have much of a presence in pop-culture.

Many analytic philosophers are respected in other fields because they make contributions to other fields. Going back to the 1900s you have the fathers of analytical philosophy Bertrand Russell and Gottlieb Frege; both of them can be considered in the top 100 mathematicians of all time. The same can be said of Kurt Godel who was a part of the movements second generation; his incompleteness theorem is considered one of the most important mathematical results of all time.

Nowadays the top philosophers are Saul Kripke and Hilary Putnam (just died). Kripke first achieved fame in mathematics where he published his first paper at 17. He’s considered the father of a field of math/logic called ‘modal logic’. He was invited to interview for a teaching position at Harvard while still in high school. Although he turned down the offer and instead attended Harvard as a student he did teach graduate level math at MIT during his sophomore year at Harvard. He’s also made some contributions to computer science which I am less familiar with.

Putnam likewise has made contributions to math and computer science, however, unlike Kripke his contributions to computer science where significant and produced the Davis-Putnam algorithm. He also contributed to the proof that Hilbert’s 10th problem is unsolvable, for which someone later won the fields medal (the math nobel).

EDIT: Also Turing.

I'm just commenting because I'd like someone to go in depth and talk about Schopenhauer.