Holding a grudge in politics is particularly foolish, says Sen. John McCain, and taking an expedient political position usually does not turn out well.

McCain has been criticized for reconciling with the Rev. Jerry Falwell, with whom McCain clashed during his failed campaign for the Republican nomination for president in 2000. McCain, considered a leading GOP hopeful for 2008, gave the commencement address at Falwell's Liberty University this month.

"I think one of the stupidest things you can do in politics is hold grudges. It's a waste of time and it doesn't do anything for you or for your constituents," McCain said on "FOX News Sunday."

Critics of the Arizona Republican see the Falwell reconciliation as McCain's bid to win over right-wing conservatives. McCain, however, said he has found that political expediency can create problems.

For example, McCain said, in 2000 he supported flying a Confederate flag over South Carolina's Capitol to avoid alienating "a certain voting bloc" ahead of the state's presidential primary. Blacks and many others see the Civil War-era Confederacy as a symbol of slavery and racism, not merely an emblem of a heritage cherished by many white Southerners.

"I shouldn't be involved in it, it was a state issue. It was an act of cowardice," McCain said in looking back.

"We're all gifted, no matter how principled we are, with the gift of rationalization. But I knew it was wrong at the time, but I rationalized it: Well, you know, I can use this as a way to avoid a political, you know, downside. And it was wrong," he said.

Asked how he knows he would not do that again if he ran for president, McCain responded:

"Well, I've learned a lot of lessons in my life. I'm older than dirt. I've got more scars than Frankenstein, but I've learned a lot of things along the way. And that was a very strong lesson for me. And there have been other times in my life. But I can tell you that I know the difference between right and wrong."