Earlier quoted context omitted.
The question I always ask when people suggest warfare, especially an invasion: will you personally fight in it?
Maybe a better question would be are you willing to allow crimes against humanity to occur if you can avoid personally fighting against it? Plus there is a whole spectrum of physical intervention if we choose to. E.g. drones, supporting insurgencies, etc... that doesn't even require boots on ground. This principle would be under R2P responsibility to protect.
Also, killing human beings enemy combatants dispassionately with drones... Not something I'm energetic enough to debate today.