Fake Alias

Well first of all I do not think of myself racist in any way. I support multiculturalism and different ethnic groups, however my friend told me some jokes the other day that were the funniest thing Ive ever heard. If I laugh at a joke that makes fun of a black or jewish person, even though I do not believe any of it, or would never repeate it, is it still wrong? Should jokes of this nature be thought of as simply a joke (even between two good friends), or is racism too serious to be joking around abuot such issues? Please dont think of me as a jerk, I just want your honest opinion of this is acceptable or discriminatory.