if someone likes a villain/antagonistic character and hits you with the "well duh, they're supposed to be terrible!" or "god forbid a character is morally grey", pay attention to how they talk about said character, and you'll see if they really like this character for being a villain, or if they're making excuses for said character.
for example, i like Azula. i relate to her (to an extent). but i will openly admit that she's an abuser. because she is. she abused her brother, she abused her friends, and she's also a sadistic war criminal who singlehandedly conquered an entire kingdom. she's manipulative, she has no concern for human life and has never expressed remorse for her actions.
i won't make excuses for Azula simply because i empathize with her, and i also won't downplay her actions by beating around the bush and calling her "flawed" or saying vague shit like "she pushes people away". she was abusive and toxic, simple as that.
similarly, i like Pink Diamond/Rose Quartz (to everyone who thinks i just despise queer women). i think she's a very compelling character. but i can still freely admit that she was toxic. she hurt a bunch of people who were very close to her, she permanently injured Volleyball, she abandoned Spinel for hundreds of years, and she traumatized the Crystal Gems and Steven for life. she was definitely more of a morally grey character than pure evil, but that doesn't mean she didn't do terrible things.
it's easy to call a character flawed or morally grey. everyone is flawed, and everyone is morally grey to some extent. no one is perfect, no one is pure good or pure evil.
it's a lot harder to admit that a character you like is abusive or a rapist, or anything that clearly defines them as a terrible person, especially if you relate to that character.
and the thing is, relating to characters like Jax or Catra doesn't necessarily mean that you're an abuser too. i relate to both these characters, to some extent. i can empathize with Jax's fear of vulnerability and intimacy. i can relate to Catra's experience with abuse and her trust issues and self-loathing.
you can like villains, you can relate to them and it doesn't make you a terrible person. but i feel like a lot of fans get way too defensive because they see themselves in this character so much that any critique the characters faces feels like a personal attack.
it's also good to introspect sometimes. do you display some of these destructive habits? have you hurt people in your life? what is it about this character that hits close to home, and how can you avoid ending up like them?
if you find yourself defending these characters, ask yourself why. is it truly because everyone who dislikes them is a homophobic misogynistic racist POS who has no media literacy? or is it perhaps because the critiques hit a little close to home and you're avoiding some necessary soul searching?