This. Exactly. In certain genres and medias, if you are a fan of a female character, you can end up spending a lot of time on the defensive. It becomes a reactionary thing because you're so used to taking shit for being a fan. You spend so much time and energy trying to explain to people (who usually don't want to hear it anyway because "ew girls!") why that character is there and why they're important to you and to the story (see Black Widow in Avengers) that when someone comes down on them, it's the go-to response.

Also there's a very good chance that whatever arguments you're using against these characters have been thrown around by people with far more vitriol and hatred toward women in general than (I hope) you're expressing and that can lump you with that group right off the bat.