Senate Majority Leader Harry Reid (D-NV) made his statement on the floor of the Senate, so I suppose he has some degree of limited immunity. But if he says, or has said, similar things elsewhere, he should be arrested for hate speech.
What did he say? Reid Compares Opponents of Health Care Reform to Supporters of Slavery "Reid argued that Republicans are using the same stalling tactics employed in the pre-Civil War era." Reid is also quoted as saying "When this body was on the verge of guaranteeing equal civil rights to everyone regardless of the color of their skin, some senators resorted to the same filibuster threats that we hear today."
In other words, he condemned opponents of his bill as being like the kind of Democrats we should have left behind long ago the kind of Democrats who maintained slavery, the Democrats who pushed secession in the face of the anti-slavery views of the first Republican president (the president who ended slavery), the Democrats who later thwarted desegregation efforts for decades, the Democrats who opposed anti-lynching laws, and the majority of Democrats who voted against the civil rights acts. The kind of Democrat like Harry Reid.
That really is offensive projection. Apparently Harry Reid thinks we should be as bigoted and ignorant as he is. And he is deploying his offensive rhetoric in support of a massive disaster of a bill (much of which he continues to hide, even from his second-in-command) that is opposed by more than 60% of the people Senators and Congressmen are supposed to represent.
I think the Democrats, and especially their current (mis-)leaders, would do better to accept the racist history of the party and learn from it and clean up their own act rather than continuing to lie about it and impugn others for the past actions of their own party.