Why do fans of a show worship the side characters but trash the main characters?

I remember looking up JoJo content and seeing tons of hate for Jonathan for weird reasons like "He's too much of a millennial" or "He's too much of a nice guy" but he's literally a character from the early 1900s. Then I look up My Hero Academia content and see that everyone hates Bakugo and Midoriya with detestable passion while thinking Kacchan is some sort of saint.<br><br>This is pretty much everywhere I go for anime and I'm wondering where the hell all this hate for main characters was coming from.<br><br>&#x200B;<br><br>Edit: Let's change 'side characters' to 'supporting characters' to avoid confusion.