I'm not overlooking anything, including the desperate circumstances that led things like the French revolution and ensuing violence. The US went through a war to be free, plenty of people died and it could have easily gone another way. If everyone followed your advice India would still belong to the UK.

I also think it's unhelpful to compare utter madness like the killing fields of Cambodia with a typical (even failed) revolution. More typical outcomes can be seen in the wake of the "Arab Spring", which arguably achieved nothing at great cost. That doesn't mean that people won't try again though, drowning people are dangerous and irrational, and I'd argue that's why leaders and people with power should work very hard to prevent those circumstances from emerging.

In a country like the US it isn't that hard.