I doubt if anyone doesn't believe ISIS is an inherently evil organisation ( although the Syrian Government has murdered far more people than it) however it seems to me defeating it is problematic.
It has to be defeated in two ways.
Directly in Iraq and Syria and thus destroy the idea of a Caliphate. The reason this is hard is if you have the wrong boots on the ground you could destroy ISIS but have another organisation as bad or worse replace it.We should always remember the disaster of invading Iraq and how it led to the creation of ISIS
Indirectly we have to destroy ISIS's ideology. Much more than Al Qaeda ISIS has been able to successfully infuse their idea of islam onto young men of many nations who then commit terrorist acts under their name although they are mostly lone wolves.
How you destroy such an ideology is something few people know how to do. I certainly do not.
I suspect this will be something we will be fighting for a long time