But haven't George Bush and other Republican politicians accepted the support of Jerry Falwell, who spouted hate of his own? Yes, but they didn't financially support his ministry and sit directly under his teaching for decades.
The better analogy is this: What if a Republican presidential candidate spent years in the pew of a theonomist church -- a fanatical fragment of Protestantism that teaches the modern political validity of ancient Hebrew law? What if the church's pastor attacked the American government as illegitimate and accepted the stoning of homosexuals and recalcitrant children as appropriate legal penalties (which some theonomists interpret as biblical requirements)? Surely we would conclude, at the very least, that the Republican candidate attending this church lacked judgment, and that his donations were subsidizing hatred. And we would be right.
Andrew Sullivan, in contrast, seems to have suspended his usually reliable critical judgment.