Fellow GOP Gov. Haley Barbour of Mississippi said he doesn't think the proclamation was a mistake.
"To me, it's a sort of feeling that it's a nit, that it is not significant, that it's not a -- it's trying to make a big deal out of something (that) doesn't amount to diddly," Barbour said in the interview aired on CNN's "State of the Union."
"I think it's unfortunate that the governor is so insensitive to the atrocities made against African-Americans in this country by the former Confederate States," said Derrick Johnson, president of the Mississippi NAACP. "As governor of the state with a higher percentage of African-Americans that any other, we would hope he would be more sensitive to them."
Barbour also noted that his state has a holiday, Confederate Memorial Day, that has been maintained by Democratic and Republican governors and the state's majority-Democrat legislature.
The governor also said he was not aware of any complaints that the holiday was offensive.
"We have always raised out opposition to any memorial day that would raise some type of positive light on the Confederacy that broke away from the United States," Johnson said. "We consider that treason."
Another objection to the day is that many people celebrate it on the same day as Martin Luther King Day, Johnson said.
"I don't really see what to say about slavery, but anybody that thinks that you have to explain to some people that slavery is a bad thing, I think that goes without saying," Barbour said.
McDonnell revised the proclamation after a day of scalding denunciations as the story became grist for cable news shows and caught fire on political blogs and in social media.
McDonnell had issued the Confederate History Month proclamation at the behest of the Sons of Confederate Veterans, descendants of rebel soldiers. McDonnell was the first Virginia governor to issue such a proclamation since fellow Republican Jim Gilmore in 2001. Democrats Mark Warner and Kaine, who succeeded Gilmore, refused.