Trained doesn't mean exercising good judgement. Just the other day one cop shot another one through his windshield after the first cop "quick drawed" the other one with a loaded gun.
I think that's an argument that it's not easy to determine who should be "allowed" to carry. Of course, there's been numerous cops who have had negligent discharges. We presume they were "trained professionals".
Personally, I'd rather give non-felons a chance to defend themselves.
The idea that cops are "trained professionals" is factually false. MOST cops do no more than the basics necessary to maintain qualification, and that qualification level is pathetic. Who says? Men like Massad Ayoob and John Farnam, and others of their caliber. (And if you don't know those names, you don't know enough about the topic to comment knowledgeably. Of course, the First Amendment says you are welcome to comment ignorantly.)
They estimate that crediting 10% of sworn police officers with being competent with guns, or even caring at all about being competent with guns, is erring on the generous side.