It's not stupid when you consider that these same Democrats, if they are elected, now vote for most of the Obama/Reid/Pelosi agenda. It's like shooting yourself in the foot because your foot itches. The strategy is self defeating because you're not really advancing the pro-gun agenda by electing the enemy even if you think they're on your side on this issue.
Then, by extension, a “single-issue” platform like the NRA’s would be similarly stupid. The NRA cannot endorse a Democrat because of what they might do on other issues, so that would negate the single-issue platform and concept.
But, the NRA IS a single-issue organization. Hedging their endorsements on other issues is simply foolish. The endorsement of the NRA should mean SOMETHING, other than a de-facto RNC stamp of approval.