At least be honest with your expectations. A lot of people die and the region gets thrown into chaos for a while but MAYBE we prevent an even worse future outcome, maybe.
That is what you're actually going for. Which is basically the Iraq argument and it turned out to be a poor decision, but this is not to say that the lesson is to never intervene. There are possible, but incredible unlikely, scenarios in which Iraq is not invaded and things somehow turn out worse. The lesson is to stop assuming the alternative to whatever strategy you have now is automatically better, it could be just as bad or worse.