The Black Legend is a real thing, albeit a highly debated one. You may be interested in these posts:

• /u/legendarytubahero describes the concept and its nuances here

• /u/drylaw histroically situates the Legend here

• I present a couple examples here

In short, "Black Legend" is a modern term for the historical trend of villainizing Spain after its American conquests. It grew out of awareness of Spanish cruelty in the Americas, but combined with anti-Catholic religious sentiment and anti-Spanish-Empire political sentiment to be both a rampant, terrible prejudice and a handy scapegoat for whenever anyone else did anything bad. "Hey!" those Anglo-Saxons might say, "at least we're not as bad as the Spanish!"

While this sentiment was certainly bad and flavored academic and sociopolitical discourse for years, it's not an easy thing to throw off. The Spanish did do terrible things. The conditions in Andean mines are still horrific; marches for miners' rights are nearly a weekly occurrence in La Paz. And yet, the Spanish were hardly unique for exploiting the labor of new subjects, particularly during the era of colonialism. Their conquest was not the total, hack-and-slash domination the Legend, and many layfolk, consider it, and nice Spanish people do actually exist.

What it turns into, and what you can see in those comments, is some kind of "Colonialist Olympics" where you cannot rest until the other guy is worse than you. Both the Spanish and British empires can't have been bad in their own right. This is the same kind of argument that happens all over the internet:

"Spain wasn't that bad, at least we still have indigenous people in Latin America! Britain killed all theirs."

"But there are natives in the US and Canada! On reservations no less! So they're more indigenous than those mestizos you try to pass off as Quechua."

"Well at least Spain never practiced slavery. There were laws against that. Britain and US bought and sold people!"

"That's pedantic. The conditions in your mines were pitiful. At least our slaves have families and traditions."

"At least ours had salaries! And we were just copying what the Inca did."

"Look at Pizarro!"

"Look at Bartolome de las Casas!"

"What about Colombus!"

"What about General Custer!"

The debate could go on. Yes, most of these statements are reliable- simplified, but reliable. But internet people gonna internet: somehow, in some magical way, someone else's wrongdoings make yours less wrong.

So yes, with reference to the answers I posted above, there is some ground for the comments. There is a history of over-emphasizing Spanish brutality. That is not, however, what John Green is doing in the video (he actually let's them off much more nicely than many other pop historians), and it does not validate their near Spanish apologism.