There is a differene if a man comes on to a women thats fine to you if your a straight women. But anders flirts where uncomfortable to straight men thats why a lot off people got angry about it.
Err, not all straight women are happy when a random man flirts with her. I know that in my second playthrough, when I wasn't planning to romance Anders, and I didn't know there was a way to bypass the flirt dialogue entirely, I winced at the way Hawke asked Anders not to speak to her that way. Mostly because I've had that awkward interaction with a man before, and I didn't know how he would take it. Obviously Anders didn't become aggressive and creepy after being rejected, but in real life, some women have that happen, or worse.
It's not fun to have to reject anyone, even if you're not worried about their reaction, but it's not a horrific injustice if a man has to do it to another man in a game, especially since there's a way around it.