Fair enough. When Iraq and Iran where going at it (in the 80s), the US supported Iraq and Saddam against Khomeini. Was that the wrong move? And then Saddam turned out to be evil. What's one to do?
Saddam was butcheting his own citizens before the US involvment. Assad was butchering his own citizens before the US (non-)involvment. Ghaddafi was butchering his own citizens before the US (and EU) involvment. Etc. I don't have strong feelings either way, but letting dictators slaughtering their own in silence is not satisfactory.
You're in massive denial if you think "westerners" have a monopoly on violence. You might want to read some history, and say how the Comanche and Apache repeatedly slaughtered each other before Europeans got involved. Violence is in our animal side, and only a racist and an ignorant would say a certain group of people has a monopoly on it.