Along with many others, I've criticized Ron Paul for not renouncing support from assorted loonies. However, at least Paul has not directly solicited their support (update: as a commenter points out, he does, however, appear regularly on "Truther" Alex Jones's radio show). By contrast, "Obama paid his respects to one of Harlem's top powerbrokers - Reverend Al Sharpton, who says he hasn't decided who he is supporting, but the meeting sent a warning to Hillary Clinton that Harlem could be up for grabs." So long as it's considered acceptable for "mainstream" candidates to actually solicit support from the likes of Sharpton, and for that matter Giuliani supporter Pat Robertson, it gives Paul supporters good reason to question why their candidate is receiving such scrutiny for merely refusing to screen supporters. Apparently, if dangerous fringe demagogues have a sufficiently large political constituency, anything goes. (In my own case, I merely pointed out that the Paul campaign's refusal to disassociate itself from fringe supporters discourages me from supporting him as a protest candidate.)
Ron Paul versus Barack Obama: