I am not shy of making or laughing about jokes that are...controversial. Hell, my favourite comedian is Hans Teeuwen :D Though I don't make racist jokes often, that would include those too, as well as woman-unfriendly jokes or jokes that are simply insensitive. It's not that I don't take racism seriously, it's that I don't take jokes seriously.
However I understand that other people don't feel that way, and I only make those kind of jokes when with people that regognise jokes for what they're worth and be able to laugh about it.
So I would either ignore them if were you and if that doesn't work, tell them that you don't like that sort of humor and ask them to tone it down when they're talking to you.