So what? Hitler did not create dictatorships. He did not create a genocide. Even on the subject of antisemitism, Hitler would quote Henry Ford who was a rabid antisemite. That still doe not excuse his actions.
So stop trying to justify slavery by claiming other nations practiced it. Sure they did but the United States fought for freedom and then created these immortal words - "We hold these truths to be self-evident, that all men are created equal, that they are endowed by their Creator with certain unalienable Rights, that among these are Life, Liberty and the pursuit of Happiness."
Did Arabs & Europeans declare that? Are you nitwits claiming that the US is no better than old European or Arabic countries? Morons.