His filibuster against the Civil Rights Act put him in this position. Had he succeeded, his impact would have been far more detrimental to the rights of those protected under the act today then anything Byrd had/has done.
Both are disagreeable sorts, but Strom's lasting impact would have been much, much worse.
See the actual text that paulv selectively quoted out of context below.
http://chronicle.augusta.com/stories/1998/07/13/met_233245.s...
Second sentence: "U.S. Sen. Strom Thurmond, R-S.C., no longer supports racial segregation."
Actual quote from Thurmond below:
"I may have said some things that I could have left off because I favor everybody receiving equal treatment," Mr. Thurmond said. "Race should not enter into it. It's merit that counts."
And in a (probably futile) attempt to stave off another misstatement of my position: I don't believe Strom Thurmond stopped being a racist. I don't believe that Robert Byrd stopped being one either.
"His"? Singular?
Both Byrd and Thurmond attempted to filibuster the Civil Rights Act, so I don't know where you're getting "anything Byrd had done" from.