If power made one evil, then God would be the Devil.
If we say that anyone who ""moralizes"" must be perfect morally then we are in effect saying no one can moralize.
Our fear of hypocrisy is forcing us to live in a world where gluttons are fine, so long as they champion gluttony.
Getting the support of Syria is the moral equivalent of winning the Klan's endorsement - it might be useful but it doesn't necessarily speak well of you.
The problem with the United Nations is that while democracy within nations is the best available form of government, democracy among nations can be a moral disaster - especially if some nations are not democracies.