Segregation was the essential point of Thurmond's program back then, the main thing distinguishing him from the Republican and Democratic candidates. If you're going to refer to Thurmond's presidential bid over half a century earlier, rather than the man's stances and achievements as a senator much later, the obvious difference is that back then he was segregated. And Lott had already made a rather similar (in fact nearly identical) remark in the past, so he must've known how it would be interpreted.

Steele, being black, could get away with it I'm sure. The others, it would probably be a media scandal as well, and some on the Democratic side might try and blow it out of proportion. That's just how politics works. The part of your post I'm disagreeing with is that you try to equate Reid's statements to Lott's, and accuse people of double standards for defending Reid while having attacked Lott. I strongly suspect that they do indeed have double standards and would attack e.g. McCain if he said what Reid said, but that's a hypothetical situation that hasn't actually happened.

What social agenda and which black leadership quotes are you talking about? The quote by Congresswoman Lee, I'll grant you, was idiotic and even incendiary, trying to cast Republican opposition to the health care bill - and Democratic support for it - as based on race.