Seems to me his gun is not the actual problem. Seems like taking his gun would just send the gun safety debate in a weird direction.
I’d say what should be done instead is the media ownership by mega-corporations should be broken up. Massively wealthy all-for-profit organizations should not be in control of our media, nor should they be allowed to donate to political campaigns (Citizen’s United), nor should they be allowed to run our utilities and energy industries without irresponsibly (see California gas leak, oil spills, Keystone XL, fracking, etc).
If actual independent not all-for-profit intelligent journalists were providing the public’s information about politics, hopefully Trump would not be taken as a serious candidate.
Also probably we need to look at how Trump is a viable candidate even outside the media profiting on his circus act’s entertainment value, and address everything we find from that, too. Why do so many people want a clown president? Why a xenophobic president? Etc. I.e. how can we correct the insanity and childishness in our culture?