So, this actually brings interesting questions to mind that would take some complicated surveying to figure out. Are there correlations between various demographics of gamer and the type of behavior seen at tables? Why did some of us see a lot of this, and others not?
Like, we'd at least to first guess expect depictions of evil lacking in nuance from players who are particularly young, because they don't have a nuanced view of the world overall, and their are still working on building their visions of the world. Giving a 14-year-old a place to "act out" may have such results.
But we can also consider how long that player has been a gamer, their playstyle preferences, the stated playstyle of the table, experience with other fiction, and so on.
I think that, lacking a real delve into the subject for data, ascribing the behavior to the game structure is jumping to a conclusion.