Let's get the most obvious example of hypocrisy out of the way first: Michael Steele says Harry Reid should resign for his statements about Barack Obama, because Trent Lott had to resign. 2002-era Steele felt differently.
At the time, instead of being the wacky head of the Republican party, Steele was just the incoming Lt. Governor of Maryland and one of the very few credible African-American Republican elected officials in the nation. Republican Senate Majority Leader Trent Lott had just announced that the nation would've been better off if Dixiecrat racist segregationist Strom Thurmond had been elected president. Steele acknowledged that that was probably not a very good statement, but it was not worth getting excited about, really.
"I know Trent Lott personally," said Steele in 2002, "and I know that this is not his intent. But it's still unfortunate. And I think he needs to apologize a little bit more.
But Steele said a resignation would not be necessary.
Republicans don't understand racism, and don't understand why they keep getting accused of it. They are very sensitive about it! They also, like Washington journalists, view politics as more of a sport than the method by which we attempt to govern the nation. So this is not about what Reid said. It is about how in 2002 Democrats won an embarrassing resignation, so it is only fair that they get to attempt the same thing now. The fact that the "scandals" do not resemble each other at all, except in that they vaguely involve race, does not matter.
(And, just for the record: a 70-year-old white guy saying the word "Negro" in public is embarrassing and regrettable, like when grampa does it. But all it means is that he is a 70-year-old white guy. In fact, as far as embarrassing racial things grandpas say, it is actually sorta proof that he is trying to be open-minded; there are much, much worse terms available.)
Now Senators John Cornyn and John Kyl are also calling for Reid's resignation! Those old white guys are so outraged about Reid's racism toward the guy that he supported and voted for in the presidential election!
Before Lott's decision, only one GOP senator — Sen. Lincoln Chafee of Rhode Island — had said publicly that Lott should step down.
Lincoln Chafee! Remember him? He was a Republican Senator from Rhode Island who was just not a very good Republican at all (pro-gay, anti-war), which is why he is now an "Independent." He also endorsed Obama in 2008.
And he was literally the only GOP senator who openly announced that Trent Lott should resign for announcing that the nation would've been better off if segregation had continued. John Kyl and John Cornyn were both Senators at the time, by the way (Cornyn took office a couple weeks before Lott stepped down as leader).
Harry Reid did not say that Obama's light skin and lack of a Negro dialect meant that he should get to sit in the middle of the bus, or only get up for college-educated whites. Or that Reid might make an exception and allow him to marry a white woman as long as she's not too white—like, maybe an Italian?
Reid used no-longer-acceptable old-man language to express a fairly uncontroversial opinion. The only person he owed an apology to is Obama himself, who, hopefully, told him that we don't say "Negro" anymore, like one would tell one's grandpa.
(There are plenty of other reasons to call for Reid's resignation, actually—like the fact that he is a weak leader facing an increasingly dire reelection campaign and he is also a conservative pro-life Mormon in charge of the Democrats for some reason.)