With Republicans trying to draw parallels between Harry Reid and Trent Lott (who had to give up the same job for his racist comments) it's good to go back and look at what Lott actually said: "When Strom Thurmond ran for president, we voted for him. We’re proud of it. And if the rest of the country had followed our lead, we wouldn't have had all these problems over the years, either." As Wikipedia reminds us, "Thurmond had based his presidential campaign largely on an explicit racial segregation platform."
I can accept having repentant and reformed ex-segregationists in our politics. That's the way it usually goes once an evil system falls and the good guys win -- you allow people who were on the wrong side (and didn't commit any real atrocities) to continue within the new system. That's how things were done in post-Apartheid South Africa and post-Communist Eastern Europe. But the price of admission is that they condemn the evil old system, wholeheartedly accept the new order, and accept that what they did was wrong. What we can't have is having unrepentant segregationists proudly defending the bad old days and acting as if they were on the right side. If the most powerful Senator is doing that, you haven't moved past the bad old days.