As you've guessed, this post is quite ridiculous, but it might be fun to have a crack at it. I'll do it in order of what s/he said so it's easy to follow, but like you I won't bother with the politics of it.

Julius Caesar (the first literal God-Emperor of the Roman Empire)

Ok so, if he means Julius Caesar (100-44 BCE) then it is indeed correct that he became a literal god after his death, not before though. If you're interested in why he wasn't the first emperor, a cursory search of the subreddit yields a ton of answers, since it's a common question.

In the Roman republic, there were two political parties. One was called the Populares (literally: "the populists"), and represented the desires of the common citizens. The other party was called the Optimates (literally: "the best"), and represented Patricians and Equestrians (read: the political elite/establishment).

This is just nonsense. First of all, the closest the Roman Republic ever came to political parties was the mob gangs under Milo and Claudius during the First Triumvirate. Second, they did not represent that Patricians and Equestrians, by this time they were mostly the same class anyway, with only the more famous Patrician families having anything to show for themselves (such as the Claudii). The Populares represented the people, or rather - more cynically - the part of the people that would yield votes, which doesn't just included a part of the equestrians, but also farmers, storeowners and such.
Using the word represent is kind of wrong in these circumstances as well, that leads the thoughts to modern day political parties and completely ignores the clientes-patrones system. If you don't know what that is I'd refer you to this post by Tiako, which sums it up well.

During Caesar's ascendancy, he was a leader among the Populares, propelled by his military successes in Gaul (the dude seriously annihilated barbarians). Cato, meanwhile, was a major voice for the Optimates, and is respected to this day for his excellent rhetoric and political professionalism.

First of all, during Caesar's ascendancy he was a middle-class nobody, certainly not a leader of the populares. His military successes in Gaul did indeed propel his career forward, but there are quite a few years in between Caesar's ascendancy and him "crossing the Rubicon".
Moreover, while Cato (the Younger) indeed was a voice for the optimates, what I've understood about him is that he was more anti-Caesar than anything else. Also, part of why he's well known today is because he was commended by Caesar, partly because of his failed-and-then-victorious suicide and also because of his ancestor Cato the Elder. I doubt any historians today look to him as a great rhetorican though, even if he admittely seemingly could speak.

Caesar branded Cato as an effeminate sexual degenerate (i.e. cuck), and Cato branded Caesar as a despot whose personal successes were irrelevant to the leadership of Rome (sound familiar?). Caesar won the election and the consulate (the Roman presidency).

Well... yeah. That was Roman politics though, Octavian called Mark Anthony a drunk, Anthony called him a spoiled little boy back. Sulla called Pompey "the Butcher", which while might sound flattering, really wasn't. It's just a preposterous argument either way.

You can read about the rest elsewhere, but Caesar turned out to be such a strong leader that he ushered in the "Pax Romana" (peace through Roman strength) for the next several centuries [---].

This one made me chuckle because it shows a complete misunderstanding of Roman history that in effect would make Julius Caesar ~137 years old, since only only Octavian became Julius Caesar at his adoption, but also subsequently Tiberius. Julius Caesar had nothing to do with the Pax Romana and had been long dead when that period of peace started. I wrote a post about it a while back, that I'd like to revisit some time because I feel it's a little short, but should give a nice view of what it was.
Also, I wanted to note that "Kie-sar" isn't correct, the latin pronounciation is more towards "kai-sar".

In short, he made Rome great again despite his rivals going so far as to assassinate him.

No. Julius Caesar never had that much power, even after becoming dictator for life in 44 BCE.

He did make one big mistake though- he built a bridge over the Rhine. Once the Rhine was no longer an effective barrier to population movement [---]

You pointed this out yourself, but Caesar destroyed his bridges (plural actually). Even so, it's a ridiculous point because Caesar was far from the last one to enter those territories. Germanicus even earned that very name because of his successes against the Germanic tribes, and Drusus also had his share of success against the Germans. Moreover, the wars against the Germans lasted for several hundred years, with the Battle at the Teotoburg Forest being the most famous defeat, already in 9 AD.
The wars hardly stopped then though and Trajan was to conquer large parts of the European mainland during his reign; and those wars also occupied a lot the emperor's time under Marcus Aurelius. It's also worth noting that the poster somehow assumes that without the bridge at the Rhine, there would've been some kind of unified force that would stand together against the moving nomads. There was no such thing, the Germans (and peoples beyond them) were no unified people at all.

I believe that's it. Feel free to ask follow-ups, but for:

Some 400-500 years later, their free movement into Western Europe led to the fall of the Roman Empire.

I'd have to ask you to repost it as it's own question for a medievalist to deal with.