A lot of people have thought long and hard about that dividing line, and there aren't any easy answers.

When radicals are opposed by the government of the nation in which they operate, things go pretty well. Local police and military take care of things for the most part, like in Europe, the U.S., and many Islamic nations.

When radicals are supported by the government of the nation in which they operate, and use it as a base for attacks in other nations, there isn't much choice other than military action. Ideally, the best long-term result would be changing the government there into one that fits into the "anti-terrorist" category, but as we have seen, "regime change" is a real bitch to accomplish.

Unfortunately, the only alternative is an endless series of "police actions," bombing terror camps, then doing it again as they rebuild with local government support. This approach gets even worse as terrorists set up their infrastructure in civilian areas. It's a lot like what Israel is trying to do with Hamas in Gaza. We can see the obvious problems with police actions, and that it seems to require a lot of repetition over the years.

BTW, all else being equal, I'd rather have McDonalds all over the world than madrassas run by radical Islamists.