Timo, I am not a person of color but I know many who are. I talk to them often. I also know many "white" (non-color?) people who are liberal, many who are conservative and many who are prejudiced or racist. I know a few people of color who are also prejudiced and racist, too. Just to be clear, at this point I am not registered with either political party but when I was previously registered with a party I was a Republican.
Is it true that one or more people who are registered Democrats could think up crazy, prejudiced, racist, completely untrue shit and attempt to spill it over the airwaves? Yes, there is no doubt about that. However, there is a definite difference in how these people would be treated once they attempted to do this -- they would be ostracized.
As you can see with the Republican establishment, the outhouse is welcome at a local rallies and likely even a state convention. I doubt it would be at the national convention, but at this point I've learned that when it comes to the Republicans don't bet on class having anything to do with their message. Romney might just be visiting it in the parking lot outside the convention center come August. The Democrats would not put up with such a display of their brethren. They might get a cackle out of it or crack a joke about it, perhaps even cracking a joke about how such idiots are even in their midst, but it wouldn't be put on display and accepted as fact. It would not be encouraged. It would not be used to generate donations.
What do Republican candidates for POTUS do (with obvious racist, idiotic shit)? They court it, they like it, they talk sideways when challenged about any claimed facts it represents -- they clearly do not disown it and neither does the GOP leadership. It makes money for them. They hope it gets votes for them. The Republicans have blatantly advertised themselves as the unsophisticated, anti-intellectual party up to the point where I can no longer see a dividing line between the GOP and the KKK. The GOP may not wear white hoods, but everything they say, do and encourage would be at home with the KKK (although the KKK would say the GOP has not gone far enough).
What is the closest thing I have seen by Democrats? To use your reference, Bill Maher recently had a small sketch in which he questioned why Romney hadn't come clean on his "other wives", which I took as assuming Romney is a Big Love style candidate who is hiding his other wives and children. It was a comedic sketch. No one else has questioned Romney having other wives. Yet, the Republicans have routinely questioned whether Obama was born in the United States even though Hawaii has confirmed it repeatedly. John McCain even corrected a woman on the campaign trail when she said that Obama was a Muslim who wasn't born in America (though McCain did not make that correction sufficiently loud, IMNSHO), but the rest of the GOP continues to let people think that Obama is a Muslim born in Kenya. They like it. They think it will get them votes. The Democrats and Romney? There is no talk about Romney's hidden wives and children. Why not? The Democratic party doesn't have enough ignorant, anti-intellectual members to make it work. They also have enough class and enough factual material to go after the issues.
Do I think Republicans, individually or collectively, are racists? I do not know, but they don't seem to mind doing whatever is required to attract racists and their money. I call that aiding and abetting, which they do often in public because they never let facts get in the way of donations and votes. There was a time when that was not so, but the past 20 years, for sure, have revealed that is what the GOP is about.