Arm the .mil

So they aren't in gun-free zones and are able to defend themselves against domestic Muslim terrorists!

Trump is for it!  Even Borepatch is for it!

Heck, I am for it. 

But just to play Devil's Advocate here...  Let's say the policy was in place 3 years ago.  The bad guy goes to that Marine recruitment center, and the Marines return fire and prevail, as they are wont to do.  Instead of 4 Marines dead and the shooter driving off it's one Marine dead, one wounded, and one dead bad guy. 

In the aftermath.  The press goes:  "The military is operating on US soil against US citizens!  Just like Jade Helm! Thanks, Obama, for arming our boys against us"   And that is just from the right hand side of the political spectrum's chattering class.

The left press would go:  "Crazed PTSD afflicted Marine baby-killers snap and shoot up a shopping center."

You really can't win.