Honestly, my reason, despite that I'm not pleased about it being a reason, is something that you said at the end of your post:
It's basically this. I've had my fair share of a handful of rude Tanya fans that even the slightest talk in a negative way, and you know that I don't ever downright insult or make people feel dumb that they like a character, they overreact to a point where I'm just exiting out of a thread just to force myself not to respond. I do not mind people liking something I don't, and it brings out an interesting discussion between someone who's a fan and someone who really isn't. But sadly, I don't get a discussion, I get insulted that I'm not a fan of Tanya.
I don't like that the actual fans of characters have gotten me to actually dislike a character, but I'm not going to be a certain user and bash them per thread they're being mentioned. I've stated before and I'll state it again that I do give characters a chance before judging them on whether or not I want to continue playing as them. And since Tanya is just DLC, I'll be waiting whether or not she's worth the money by watching a few videos. Granted that it kinda defeats me saying, "don't judge what you haven't played" but I think I'm missing something to my reasoning in this situation.
But I will say, my other reasoning for not liking her, I disliked what they did to her in Deception. She's basically one of the main reasons why the events in the fourth game happened. But then, she partners up with the Deadly Alliance and did nothing despite that she just wants to be called "ambassador." Then in Deception, the only thing useful that she had was that she had knowledge of some Komidogu information left in Edenia. She was basically useless and I felt that her inclusion was just kinda... meh. I really wasn't that into seeing her rise from the darkness.
Of course, they clearly can make her story become something more interesting than just constantly betraying one after the other. It's kinda... well... despite that it's her character, it's kinda becoming repetitive and I would really like for her to do something else. Something that will obviously make her become something.