People who post (or say) such things fail to understand that their racist and sexist jokes aren't funny. Posting them isn't an act of noble defiance against tyrants who would end free speech. Such jokes are invariably tired tropes, entertaining not in their cleverness but in their still-potent power to hurt. And those who take offense at them generally argue for mental filters not legal restrictions.
|The first page of a Google Scholar search for "Sexist Joke"|
However, hurt feelings generally aren't enough to convince jerks to change their ways, so it's time we delve into science. Study after study has shown that discriminatory jokes—in the case of most studies, sexist ones, but the same principles apply to humor of the racist variety—hurt their targets and help perpetuate prejudice. They create an atmosphere of acceptance of discriminatory behavior, and help make bigots feel welcome. Those studies, and many, many others, show conclusively (inasmuch as one can be conclusive in the social sciences) that discriminatory jokes make people more likely to discriminate in a number of different ways. The science is pretty well in on this issue, as the first page of a Google Scholar search shows.
Frequently, defenders of bigoted humor argue that they're being ironic, and that "like, man, we have to make fun of this stuff or it will never go away." However, they never seem to present evidence to back the idea that saying such things ironically is any better. Absent such evidence, it seems unlikely that the manner in which the speaker/writer intends their discriminatory jokes matters much—after all, it seems very unlikely that the social scientists who conducted the studies linked above really meant the sexist jokes they told in the course of the experiment. Moreover, it's very easy to miss that a joke is meant ironically unless one knows the teller quite well, which means that even if the defenders are correct, they're correct only with relation to tight-knit groups. On the internet, especially, an "ironic" joke and a joke intended to hurt a less privileged group look exactly the same. It's clear, then, that "ironic" discriminatory humor, by and large, doesn't help break down discrimination. Rather it provides a back door, a culturally acceptable route, through which to express and reinforce bigotry.
Another defense commonly offered for prejudicial humor sounds something like "my black friend doesn't mind it." Those who offer this defense have clearly never thought about the issue very deeply. Those of you who, like me, have the luxury of not worrying overmuch about discrimination should take a minute to imagine being a woman or a person of color in a world where the great majority of those in power are neither. Imagine wanting to join the popular bunch at school, a group dominated by white males. Hell, imagine just wanting acceptance from your peers, the great majority of whom are probably white. Wouldn't you let bigoted jokes slide past for the sake of not drawing attention to your differences? Might you not even pretend to enjoy such jokes as a way of fitting in? Eventually, you might even convince yourself that you're one of the good girls/people of color, more like your white, male friends than the people mocked by the jokes you now tell too. Whether this sort of alienation is rare or common, and I would argue that it is quite common, how can one honestly claim that the humor value of tired old prejudicial tropes outweighs the psychological damage they can cause?
So, what do we do about these jokes? Their defenders think "the liberals" or "the feminists" want to ban them, and so they portray themselves as heroic crusaders against censorship. They entirely miss the point. No one says they can't tell bigoted jokes to their hearts' content. They just shouldn't. There's no need for "PC Policing", all we need is individuals telling other individuals not to behave like asshats. We all have filters that keep us from saying outright offensive things whenever they happen to pop into our heads, society just needs to stop accepting jokes as an exception to the rules of what's okay to say.
So next time you hear a sexist/racist joke, even if the teller prefaced it with "I'm not racist but..", even if you know the teller probably doesn't mean it, take a few seconds to say "not cool, yo".