That's the difference between real nice guys and fake ones, obviously.
My little brother is one of these "fake nice guys". He truly believes he's a nice guy, yet he's the most sexist, obnoxious guy I know. He'll make any claim against women without even thinking about it, calling all women whores or whatnot just because some of the girls he knows like to flirt with people or have already had sex (16 years old btw).
And then there's me. I don't want to call myself the nicest guy in the world, I'm not, I've done some things in the past that I'm not proud of, but I'm definitely the nicest guy around. Especially now that I've learned from past errors and have since corrected myself.
Never would I do a single thing to harm a women, nor a man (unless either of them did something serious - and I mean
serious). I'm also not that bitter about the world at all, I'm just scared of it a bit. So much required to simply live - kinda scary at times.
Anyway, nice guys do exist, but true nice-guys are extremely rare. Easiest way to find them is in a nerdy gaming community