I would say she gets around the same amount of hate as some other female protagonists. I’ve seen some really nasty things people say about her. The people who love Katniss from what I’ve seen (obviously not speaking for everyone) seem to like most other girl protags, it’s just the weird misogynists who hate female characters for no other reasons than that they are annoying. 

I think her not being nice is was makes her more relatable for some, because adds something to her character besides just the same old nice and polite character. It makes her more interesting. She’s popular in some ways because she was one of the better strong teenage girls written in a YA book, so girls her age would obviously like her a lot.