For me, it didn't mess up my brain at all, it showed me a much broader range of what humanity really is, which is exactly what I wanted to understand at that time. I understood the depravity humans will exact upon others, or those they see as lesser (such as the treatment of animals, or prisoners, "the enemy" whoever/whatever that may be). I also saw unfiltered sharing of valuable knowledge, science, tech stuff, software, games, music, culture...

The uncensored internet taught me more than I could ever have been taught in school, and I'll be forever grateful for that. It didn't take me long to understand that I could generally hate no ethnicity or people or country, and the people who do are manipulated by their government or other powerful figures in their life (or disproportionately swayed by experiences in their life). Humans are pretty much all the same, we all have far far more in common than we do differences. I have a stronger perspective of this than my immediate ancestors (demonstrated over and over throughout my life) and I do credit my exposure to the open internet for a huge amount of that.

There is one huge and problematic difference now, though: the uncensored internet of the 90's is nothing like the disinformation-saturated internet of today.