Have you spoken to a professional about any of this in the past. I think a therapist/psychologist or somesuch might be able to give you coping techniques about how to deal with it when you're out and about.
And if you can find someone who specializes in EMDR, I'd go for that. EMDR has been shown to be an extremely powerful tool for dealing with PTSD, which it sounds like you might have (it's been tested as a therapy for lots of different kinds of PTSD, from combat-related stuff to mothers with birth-related PTSD, I personally found it very helpful in processing childhood abuse).
I don't think an anti-gun stance is unreasonable - I'm also very anti-gun and won't knowingly spend time in a house where I know there's a gun. But you can't actually change what's going on on the street, so if you can find a way to work through your reactions to seeing guns so you're not afraid to be outside in your community, that would probably be the most helpful thing for you.