Ironically, conservative intellectuals have argued against notions of "moral equivalence" for decades. Echoing those critiques, it is possible to establish a reasoned moral hierarchy between Reid's comments and Lott's. Looking at the content, context and intention of the statements, it's clear that the two cases are not equivalent and offer no evidence of a double standard at work.
In content, Reid argued that a black candidate has better odds of winning if he is "light-skinned" and doesn't speak in "Negro dialect." As I argued in my piece "Was Harry Reid Right?," scholarly research and common sense suggest both statements are true. Though many commentators have interpreted Reid's remarks as approval of racial bias in America, the quoted statement suggests nothing of the sort. There's a difference between observing a fact about how voters discriminate and agreeing with the discrimination. Or, put another way, talking about race is not the same as saying something racist.
Contrast that with Lott, who at Strom Thurmond's 100th birthday party (broadcast on C-SPAN), said: "I want to say this about my state: 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 all these years, either." There is no way around the fact that Lott was strongly endorsing Thurmond's segregationist Dixiecrat Party, which broke away from the Democrats in 1948. At the time, Thurmond's party platform included the statement, "We stand for the segregation of the races and the racial integrity of each race." In sum, Lott's speech supported an explicitly racist party and movement without any reservations.
Moral equivalence? Nope.
For context, consider Reid, who has no long history of making racially biased comments or "proudly" associating with bigots (though, I'm curious about what Reid, who is a Mormon, has to say about The Church of Jesus Christ of Latter-day Saints racist past). Even Reid's antiquated use of "Negro" isn't in-and-of-itself problematic. (See The United Negro College Fund or the National Council of Negro Women.) "Negro" can be a term of endearment from one person and an epithet from another. As I read Reid, he's simply looking for a way to refer to the distinctive intonations and pronunciations of black English. If there's evidence to the contrary, I'd like to see it. More broadly, since the mid-1960s, Democrats have largely avoided appealing to anti-black sentiment in their campaigns and policies.
Lott, on the other hand, had a 40-year history of affiliating with groups that endorse racial segregation, condemn intermarriage and oppose immigration by non-whites. In particular, Lott was a longtime member of the Council of Conservative Citizens, a spinoff of the Southern white Citizens Councils that were known as the "uptown Klan." Lott spoke at their 1992 national convention and received them in his Washington office in 1997. And more generally, Republicans, though the party of Lincoln, have over the last half-century regularly appealed to anti-black sentiment in their campaigns and policies. The most famous example was George Bush's Willie Horton ad, but other examples abound. (Bob Corker's ad against Harold Ford in 2006 is a recent example.) Guilt by association would be unacceptable in a courtroom, but it's completely reasonable to look at the totality of someone's behavior over decades in evaluating fitness for national leadership. Lott's lifetime of personal associations and party activity regularly involved harnessing racial antipathy for political gain.
Moral equivalence? Not a bit.
Just as conservative jurists attempt to divine original intent when evaluating legal doctrine, Reid's and Lott's respective intentions matter, too. On the whole, Reid's comments appear to be explanatory rather than derogatory. Reid, who endorsed Obama before his 2008 statement, doesn't offer any indication of malice or mockery in his descriptions of the candidate (as compared, say, with Rush Limbaugh's broadcast of "Barack the Magic Negro").