On average, our membership is FAR more educated in firearms and legal/constitutional issues than is the general public. That is by far the biggest difference between us and the general public. Plus, we are by definition, the "enthusiasts", which also lends to different polling.
That seems to be the most plausible explanation for the polar opposite responses.
Interestingly in the Quinnipiac Poll, it appears that the college educated NRA members are more more likely to agree with additional laws and more likely to oppose armed police officers being placed in public schools.
Its disconcerting to see that minds trained at the collegiate level appear to lack such critical-thinking skills.