Contrary to the common caricature, not all NRA members are crazed, government-hating militia members. Many members are simply law-abiding citizens, some not even gun owners, who seek to protect a constitutionally guaranteed right to bear arms.
The staff notes that NRA members "compose little over one percent of the population yet five percent of regular voters." If NRA members exercise their right to vote (how dare they!) and donate to a group that makes their voices heard, then more power to them.