Actually they do. Do you know how many classmates I've observed fall for a bully even when the bullied turned on them too? Some one acting bat shit crazy like a manic pixie dream, then showing an ounce of kindness drives the puberty mind nuts. Especially cuz we don't know that crazy and draining love is not good love. Him judging everyone and hating the world while still wanting to be accepted is also very high schooler. Even those times when he's randomly rational
There are a lot of people, especially teenagers, who think that way, though this is obviously exaggerated for the sake of the story. Self isolation is still isolation, and you can hate the people around you while also seeking validation and even scraps of kindness from them.
That was so cringe, why is he smiling, blushing and crying like that???? I find it hard to understand the way he thinks, his thoughts are so weird, no highschooler would think like that.