I'm well aware of the issues leading to war in most if not all cases, but there were still peasants starving to death in Soviet Russia after the revolution while bureaucrats ate enough food in one meal to feed a family for a week. The English, French, Russian and Chinese Revolutions didn't work out quite the way people living in the country at the time imagined it.

The only revolution in modern history that's actually stuck is the American revolt against the British, and the only reason it held is because they realized that people in positions of power are always going to abuse that position, and that people, as a whole, are ignorant and corruptible. No other violent revolution has managed to last more than a few generations, if not shorter, before collapsing under itself when people realize that replacing one dictator with another won't solve anything. Cromwell, Napoleon, Stalin and Mao were all despots who might have improved the standard of living for some, but that doesn't change the fact that for many, things were just as terrible if not worse under the new regimes than they were before.

I'm not saying that America, Britain and the other Allies should have just rolled over or tried to bargain with Hitler, instead of trying to stop him, but in the case of revolutions, historically the cost of nonviolence has been about the same if not less steep than the cost of actually toppling a government through force, and I'd still rather work to solve the problem rather than replacing one dictator with another.