Well, when you read the write-ups about their annual meeting, one gets the impression that if you are pagan and anti-war, you might not be welcome
I honestly never thought I'd be saying this to you, but maybe you just need a thicker skin. For one thing, I kinda doubt anyone at an NRA meeting will be asking you to confirm your support for non-gunnish political positions, or making you pray the rosary with them. I've been to a couple of their annual meets, and I didn't get the impression that it was a prayer meeting or a pro-war rally.
That being said, I don't know what you've heard, and my attendance at the meetings was pretty much limited to the trade show aspect of it (the manufacturers' exhibit hall, or whatever they call it).
My fellow Christian conservative types have the same complaint about a lot of organizations, one in particular is the university. I think they need to get a thicker skin and not be so worried that the profs are all politically backward.
In both cases, I think you'll find you're not the only oddball in the bunch.