Going by the analogy that the OP is not actually trolling and is being serious then I would point out that this is a very complex subject. Some people have already shown that they understand that. At the other end of the extreme there are people in this discussion who have proved that there are people opposed to ISIS who are even worse than ISIS members themselves. People like that are the ones who will escalate problems.
From a balanced perspective - ISIS is not a person; it is a group of people and an ideology. Also, note that it is also not just led by one person. Cut off one head and another will spring up in its place. It cannot be killed but it can be exacerbated by techniques like indiscriminate killing of innocent people under the ideology that "people in poorer regions of the world are all alike and of less importance than westerners!" In other words the "bomb them all" kind of mentality will make things worse.
There are posts from people on here that indicate that certain people do not respect life - those who think they they can just eradicate an ideology by blowing people up left right and centre with no regard for non-combatants like children. They are here to remind us that some of the people opposed to ISIS are basically the same as ISIS or worse.
We also have people who are implying that ISIS are "Islamic"... and yet Muslims are one of the main casualties of ISIS. This is both from the perspectives of Muslim people being killed by members of ISIS and Muslims abandoning Islam to join ISIS.
ISIS (as an ideology) itself is rotten to the core - I highly doubt that actual negotiation can occur with any one of those who actively support the central ideology of ISIS. I would suggest that one of the only ways to quell things like ISIS is to not feed it - to find ways of preventing people from joining it or similar groups... which is of course incredibly difficult (especially with the people trying to kill an ideology by killing people).
I have noticed that no one has mentioned the likelihood that ISIS could actually be funded and supported by certain people in western governments indirectly (USA, UK, etc). I am neither saying that this is true or not, I am not fueling a conspiracy here - I am simply implying that this kind of thing (things like ISIS) provides western governments with the ability to justify certain actions. If that is the case, and this is being funded by westerners in order to justify exerting more control over its citizens, then this would be even more complex.
Ideologies like ISIS will probably never die. Humans, on the other hand, all die though. It is how we live that matters (and maybe the way we die as well).