Because freedom of speech is the most basic and important freedom we have left in the electronic age.
It may well be the ONLY freedom we have left, and, at that, it's pretty much confined to comedy anymore. To censor comedy, is to censor life itself, particularly when that censorship comes from people who don't even understand what's going on when comedy goes down.
Now...
It's kinda beyond awesome that I lost a reputation point for posting Dave Chappelle. I have not laughed that hard in years. Some people just don't get humor do they? (I'll explain that at the end).
In the US, Dave is not considered 'a good black comic' he's ranked up there with Richard Pryor, the Smothers Brothers, Dick Gregory, Mort Saul, Rowan and Martin, and Lenny Bruce as people (who like Lady Gaga) are/were trading art for politics and used their art to make a statement. Like Stewart and Colbert do. (Which by the way is what The Simpsons, Family Guy and South Park do too. Look up 'satire' in your on-line dictionary).
Now, tomorrow I'm going to hang stuff in the Cow Palace with my rigging buddy. We've been working for over a decade now together as a team. I trust my life (really, I'm 55 feet in the air, sitting on an I-Beam, or he is) to him, as he does to me. And I'm going to tell him about this. I'll have to do it a good 15 minutes before I start because that is how long it's going to take him to stop laughing and stand back up again. Oh yeah, he's AA, and I'm a honky, at work they call us 'salt 'n pepper' - as in 'Get Salt and Pepper to do that' because flat out, we're the best riggers ever. But he will love it.
Now, the deal with those shows is that pretty much, and I think because of people like the most puritan among us, those that are really what the jokes are really about (I'll explain that at the end) for the most part, the ONLY way to criticize 'the system' is through comedy, cartoons in particular. There is no real political commentary left on TV outside of cartoons and Stewart and Colbert, and that's exactly what this is, political commentary as curve ball.
So, here is the real joke in the Clayton Bixby sketch, are you ready? The only people who find that racist, are....
Because the only people (in the USA) who would find that offensive are the white, trailer trash, white supremists, KKK members - because that's who it's making fun of. Not black folk.