> Maybe making fun of gay people has a history that includes discrimination and abuse, even jail and murder? Maybe making fun of white people does not have the same history

depends on where you live... there are some african countries where discrimination and abuse of white people is defintely part of modern day history though it may not be politically correct to say it in the united states. an eye for an eye makes the whole world blind (which is kind of the implication of your humor ethics)

also while we are talking a fun fact: most capital investment goes into capital turn over, replacing stuff. So most wealth that exists today was created in the recent past and not as the result of slave labor or something (your ethics might not make as much sense as you think because entropy is a thing)