As a person who has ran into a lot of discrimination for various things beyond my control RL, I can say that when it happens IC it all comes down to one thing:
Is the person doing it being a dick OOCly too.
The quickest thing to make it be an issue OOCly for me is if the 'discriminatory' character says:
I am just playing in character. The character is racist.
And then just uses that as a defense for anything, and to try and get out of any ICC due to their ICA.
At that point the character is not the only asshole present.
I am playing a bigoted character, but it is mild, and will be more of a social thing than anything else. Will it affect her RP and story? Absolutely possible, I certainly hope so, maybe she will one day even grow out of it. Maybe not.
What I will /not/ do is use it as an excuse to attack other PC's or justify ruining a scene, or make it the /focus/ of a scene because no. It might be a thing but if it turns the PC into nothing but an Antagonist it's not really /adding/ anything an NPC couldn't do better.
I remember playing on a Western game way back when (Not sure if it was @faraday 's Sweetwater Crossing or not) and it /was/ a disconnect to the theme, which can be a major turn off, when nobody seems to be playing things the way theme says things are.
I wanted to play a minority who would do awesome and great things in /spite/ of her race and gender, which is very appropriate for the setting but... it didn't turn out that way IC.
IC discrimination should be handled ICly, but by the same token, nobody can be forced to RP with someone or something they don't enjoy. If my PC's bigotry becomes an issue that causes her to be excluded, then that is on /me/ and I won't take offense to that.
I /chose/ to play a bigot, that means I get to reap what I sow.