Rather weak rebuttal.
Andrew Young was not only mayor of a major American city, he was a representative to the United Nations and still is a major figure in Democratic circles. He is a nationally and internationally known person.
But, most importantly he is considered a leader in the civil rights arena. And for a civil rights leader to make those kind of statements seems to me much more serious than an actor making drunken slurs.
No matter what Andrew Young did in the past, he is still less known than Mel Gibson. I remember when Hillary made the comment calling a guy a "dirty Jew bastard," that was all over the press even more than the Mel Gibson story was.