If you’re an activist and someone pushes you downs a guns & ammo path, you should probably assume that person is cop or spy.
And yes, I’ve mentioned this before: If someone in your group promotes any kind of violence, you should ask, loudly and publicly, Are you a cop?
Even if the person is just an idiot (as opposed to agent provocateur), by calling him or her out you highlight how the police/feds have attempted to short-circuit activist movements by pushing them toward violence, and illegitimacy.
This isn’t paranoia; it’s just good sense.
AbsurdBeats 
Depends on where you are. Police might not have to identify themselves. Especially if working under any sort of cover or plainclothes assignment. In fact, what if that person is not a police officer but a confidential informant, seeking to sell you out, to gain a blind eye and bad memory of police for something the informant did as a crime? Could also be a Fed. Could also be a “subcontractor” of the federal government.
Oh, yeah, any decent CI or cop will deny—and that’s fine. The point is less to rootch ’em all out than to foreclose any possible nastiness.
I think any kind of effective activist organization which involves foreign affairs/national security/the financial system should expect infiltration. I know it sounds faintly ridiculous to write that, but there’s just too much evidence that cops & feds do keep track. In any case, the point is not to freak out about it or spend any time whatsoever trying to figure out who might be a cop; rather, be as open as possible, and keep an eye out for, er, problematic suggestions. Then call it out and shut that whole thing down.
But when you talk about destruction. Don’t you know that you can count me out…
have you read Wendy Brown?