Bill Clinton on Robert Byrd's role as Exalted Cyclops of the KKK:

"He once had a fleeting association with the Ku Klux Klan, what does that mean? I'll tell you what it means. He was a country boy from the hills and hollows from West Virginia. He was trying to get elected," former President Bill Clinton said of Sen. Robert Byrd. "And maybe he did something he shouldn't have done come and he spent the rest of his life making it up. And that's what a good person does. There are no perfect people. There are certainly no perfect politicians," he added.

Yes, maybe, Byrd shouldn't have joined the Klan.

For the record, Byrd wasn't simply racist out of political convenience (not that that would be any more tolerable). As Michael Barone writes:

He filibustered for 14 hours against the Civil Rights Act of 1964. The interesting thing is that this wasn't politically compulsory in his state. His West Virginia colleague Jennings Randolph voted for the bill.

Jonah Goldberg argues that Byrd "was a powerful man who abandoned his bigoted principles in order to keep power"

The common interpretation is that Byrd’s is a story of redemption. A one-time Exalted Cyclops of the KKK, Byrd recruited some 150 members to the chapter he led — that’s led, not “joined,” by the way. (If you doubt his commitment to the cause, try to recruit 150 people to do anything, never mind have them pay a hefty fee up front.) Byrd filibustered the 1964 Civil Rights Act. As Bruce Bartlett notes in his book Wrong on Race, Byrd knew he would fail, but he stood on bedrock principle that integration was evil. His individual filibuster, the second longest in American history, fills 86 pages of fine print in the Congressional Record. “Only a true believer,” writes Bartlett, “would ever undertake such a futile effort.”  Unlike some segregationists’, Byrd’s arguments rested less on the principle of states’ rights than on his conviction that black people were simply biologically inferior.