Social network algorithms doesn't care if you like or not the content itself, what matters the most to them is how long your screen stays parked on a post.

Maybe you're watching something you think it's terrible, and then you enter comments to see how people are reacting. It might be making you furious, but that makes it, mathematically, a successful post that grabbed your attention and therefore the algorithm will throw more of that shit at you, because it wants your attention.

It is evil because it ignores human nature and it doesn't measure how you feel about it. It rewards highly controversial topics because it knows these posts grab people's attention one way or another.