Everyone stop taking hysteria juice.
We are not at war. A small group of petty criminals have adopted a brand. They cause far fewer deaths than Saturday night punch ups do. They cause far fewer deaths than just about anything in fact.
This is not to say nothing should be done. It should be possible to obtain a warrant for email communications. Hiring a few more police might be a good idea.
The idea that these people are any sort of big scary threat to anything, though, is daft.
You're not seriously comparing being run over at 50mph or having tthroats slit with a punch up.