Here is the www.senate.gov link to the Constitutional and historical background for expulsion and censure in the U.S. Senate. Since McCarthy was censured in 1954, only 3 men have received the punishment, and all of them basically for bribery in one form or another.

In this context, censure for racist comments seems extreme. Especially considering any Mississippi voter who cared would have noticed by now. But dubiously ethical money grabs seem to have been accepted practice by 1979 when the Senate censured Talmadge (D-GA) for taking undeserved reimbursements, and in 1990, when the Senate censured Dunberger (R-MN) for taking gifts from all comers. So the fact that the Senate that hosted racists like Helms and Thurmond until retirement shouldn't deter them from censuring Lott.