Interesting topic. At the end of the day banning someone for expressing their (possibly bigoted and offensive to a party) opinion isn't going to solve much. If it is a repeat offence after being warned I'd say it's worth punishment. However the whole thing is a deeper issue that roots itself in lack of responsibility over the internet from a reduced fear of repercussions. But here's where we can change things, these forum threads.
Examples for thought:
Should you punish someone if they call someone who turns out to have a mental condition a 'retard/sperg' for some kind of mistake they made in-game?
Should you punish someone who calls another player a 'fucking friend/nigga' on the basis that their character is black and killed them (rage), if that person is black themselves?
How about a person gloating over another they have defeated in-game using fairly fresh historical events such as genocide as comparisons, where the party the comment is aimed at turns out to have suffered second-hand from aforementioned event?
*edit*
Personally I don't think it should be ignored/just taken. Warnings and punishments should be issued, with explanations. But also dead chat is a good place to debate these things. Imho.