We could:

Send them over to Twitter and insert them in the middle of an Iggy Azalea vs American hip-hop/respected shoe designers/whoever else she hates today rant. After a few hours of reading that badly spelt stream of idiocy they'll all behead themselves. Problem solved.

or

Elect someone at DU who talks about ISIS a lot when they're not scouring the globe to locate that elusive 'moderate' Muslim (not my words) to start a massive thread in GD about how much ISIS suck. That won't sway ISIS, but when they spot the obligatory cute kitten thread that's sure to be lurking on the front page of GD they'll see the light and realise no-one's going to allow them to adopt a fur baby when they're running round beheading people and being all murdery.

No. Wait. Yr talking about what the US and not DU should do? I'm not sure it should do much else than what it's doing now. Going in there all guns blazing and killing lots of civilians for some reason might not go down well with the locals that the US would be trying to protect.

This song's for all the keyboard warriors out there. It has things in common with them...