I understand the sentiment that Rep. Carson (D-IN) is feeling when he says that Tea Party Congresspeople view blacks as "second class citizens" and wants to see them "hang on a tree," but that type of language is so far beyond reasonable that even I need to call him out on it.
There are unquestionably race issues with the Tea Party, but it isn't the 1960s style lynch and segregate racism as Carson is implying, after all they are perfectly willing to embrase blacks, such as Rep. Allen West or Herman Cain. But it can easily be argued that the Tea Party loathes "otherness" in all its various forms. Beyond their race, West and Cain are not all that "other."
But look at President Obama, he is in many ways the personification of all their fears in one neatly put together package. For one he is black. He was raised in a non traditional family and grew up partly in a foreign nation. He is well educated, went to elite universities and is decidedly urban. He also happens to have views well to the left of theirs. In sum, he is almost the exact opposite of the average Tea Partier. He is just about as "other" a person as they can imagine. In fact the only way I think he could be more other to them is if he were actually a gay Muslim.
Unlike the average progressive, Tea Partiers are unable to cope with the otherness. They reject the concept of otherness all together, and refuse to believe that such an "other" can be their beloved nation's leader. They view such an "other" as an illegitimate leader. The way many will express this is by embracing crackpot conspiracy theories, like birtherism or Obama as a secret Muslim, that would allow them to justify their rejection of Obama. They don't want Obama hanging from a tree, but they don't want him leading the country either.
When prominent leaders like Carson use such inflammatory language however, the subtlety of the Tea Party's true racial baises are washed over in the backlash. Once comments like these are made, any questioning of the Tea Party whips them and the media into a "ZOMG THEY CALLED HIM RACIST" frenzy. The nuance is lost, truly frightening, highly authoritarian beliefs of the Tea Party are left unexplored. That to me is unacceptable.