I remember that... and there was a lot of chatter about that (that was right about the time I started getting involved with OC on opencarry.org, before MOC was around), but in no way do I ever remember hearing anything about the NRA being involved.
From what I remember, it was just another person, like you and me... exercising our rights and knowing the law better then them.
And... I don't think the NRA has ever really been keen on the whole OC thing (correct me if I'm wrong, I'd love to hear that the NRA supports it!)