Why do you think they need therapy?

A question. Don't fight. Why if someone - anyone - likes a negative character, saying they find them interesting perhaps on a psychological level, is supposed to go on therapy? Obviously, they also tell you that they don't excuse their wrongdoings fictionally just as in reality, so they would be horrified by it in real life. It could be a murderer, rapist, thief, abuser, etc.
Why this person is supposed to need therapy, if they're just saying they find interesting a character? I mean, I've been liking villains or negative characters my whole life. Lord Voldemort, Death Eaters, Hannibal, Darth Vader, etc. I wanna keep this short, so yeah. What pushes you to claim they need therapy? It's something that happens only nowadays, when I was younger everyone stanned villains. No one had a problem with it. IDK.