I'm sure for most of them they have no idea how to buy a gun, and hopefully any FFL holder would recognize the mental instability and refuse service. But for any who can get their hands on one, they're not likely to be very effective, and if they try to go after Trump supporters they'll be put down quickly by someone who's carrying and know how to use it. I'd be more worried about arson. A gas can and a lighter are much easier to procure, and the deranged malcontents can do a lot of targeted damage by setting houses with Trump signs on fire in the dead of night.