Understanding the history of the rise of ISIS might help us avoid similar situations in the future, and it might help us to reconcile with them if such a thing

Understanding the history of the rise of ISIS might help us avoid similar situations in the future, and it might help us to reconcile with them if such a thing is even possible, but mere knowledge alone will not defeat ISIS. It may be that their movement is unsustainable and will wither away on its own, or it may be that local forces will eventually be able to defeat them, but if not then either we will take action against ISIS at some point, or we will have to coexist with them. Considering that this is a group whose express goal is the assimilation or destruction of all human cultures not their own, peaceful coexistence seems unlikely. (To be clear, I don't consider ISIS a global threat obviously, but they are certainly having a great deal of success locally at the moment.) The West is so morally compromised here that it's hard to imagine that we could credibly (in the eyes of non-ISIS players in the region) take action against them, but that does not mean that destroying ISIS is not the right thing to do in theory. It just means that we probably can't do it. That's not a defense of ISIS though, it's an indictment of many decades of utterly stupid and short-sighted policy in the Middle East.