As KyJim pointed out, there is nothing to this story. It is little more than an attempt to divide gun owners. The NRA has a 76-member Board of Directors, and not suprisingly given the conservative support for the Second Amendment, some of them are conservative.
However, by no means all of those members are... you may remember past NRA Board of Directors such as Rep. John Dingell (D-MI) (who would later throw us under the bus for the AWB and thus become unpopular with the NRA). Rep. Harold Volkmer (D-MO) was a member of the NRA Board of Directors until his death in 2011. Roy Innis is no longer a Democrat, having switched to the Libertarian Party after unsuccessful primary runs against Mario Cuomo and David Dinkins; but he is not exactly a conservative.
You can bet that current sitting Board of Directors members, like Rep. Dan Boren (D-OK) (who I might note addressed the NRA Annual Meeting in 2008 AND 2010
for those who were complaining about the current lineup), would be screaming bloody murder if the NRA was using member funds to promote the Republican party.
It is the height of irony that as recently as 2010, this board was alight with irate conservatives complaining about the NRA taking an exemption on the DISCLOSE Act and giving favorable press to Sen. Harry Reid and now here we are in 2012 and people are complaining that the NRA is too conservative and linked to other conservative causes. That right there is fairly solid proof that the NRA is about the Second Amendment - both sides are mad at it because it won't identify more closely with their causes.