Saddan wasn't attacked for "killing 10,000 Kurds using Sarin gas" - when that happened he was a loyal ally being backed up and supplied by the US (with the UK running along behind and wagging its tail).

And it should also be remembered that after things had changed around a bit, Syria was still seen as a good friend, and a very handy place to send "rendered" captives for a bit of extra-special interrogation.

Imagining that somehow the lines between goodies and baddies leaves our lot on the goody side is just naive nonsense. And in fact when it comes to killing non-combatants around the world we are far ahead of the highly unpleasant people we are fighting. That's not because we are more wicked, it's because the technology we bring to bear is far more lethal.
...............................

In past wars the cost to us of our own people being killed has always been a potential constraint on what we have done. With drones that ceases to be the case.

It is virtually certain that one consequence will an increase in terrorist attacks on us in the places where we live. I'm sure it will be as rationalised as the only logical way to restore that constraint.