I would say that the terrorists are the people the NRA ad is warning about. A Bernie Sanders resistance fighter was the hitman at the Republican baseball practice, Left wing protesters are the ones shutting down free speech at universities and colleges around North America. Left wingers ( some of them paid by DNC operatives) are the ones going to Trump events and attacking Trump supporters, including women. 
Left wingers have beaten Trump supporters to the ground, pulled them out of their cars, dragged them, egged them, drawn blood. The left is out of control. They call for revolution almost daily on major tv channels.