I really don't know how one can kill an idea or religion for that matter. Radical Islam won't be cured by just killing people, unless you killed them all and removed every bit of literature from the world. I"m not sure that is really feasible.
The next best thing in my opinion, is to keep them isolated, economically poor, and keep them fighting with each other.
I'm pretty sure that has been part of the policy of previous administrations.
Letting these people into our country, like France did is a huge mistake. There are "No Go Zones" in France, local muslim areas controlled by muslims where the police won't even enter. They implement their own Sharia law in these areas.
If you really value your freedom and way of life, you have to take a hard stand against accepting refugees.
The way that religion is structured, you can't have a dialogue and negotiate some sort of agreement.