It all started to go wrong in the 1960s. As part of establishment efforts to spite the Black Panthers -- who in 1967 marched on the California State Capitol building as part of a pushback against efforts to restrict the rights of black people to own guns -- the NRA sponsored the Mulford Act, which banned the carrying of loaded weapons across California. They also sponsored the Gun Control Act of 1968, a piece of legislation which restricted the shipping of firearms and ammunition, placed a minimum age requirement on gun purchases, and banned drug addicts and the mentally ill from owning firearms. You'll note that two of these three measures appear to have stuck around.
The group's support for these bills caused a hardline faction to form within the NRA that was, to put it lightly, a bit miffed at how their supposed Second Amendment rights were being signed away without a fight. They issued a simple demand to the NRA leadership: Stop the education programs and start seriously lobbying against gun control, or else. The NRA called their bluff and pressed on with efforts to relocate from Washington, D.C. to Colorado, thereby completely disengaging the NRA from politics and, as a happy bonus, flipping the most ostentatious middle finger possible to the hardliners -- who, it must be emphasized, had no possible line of recourse.
On May 21, 1977, at the NRA's annual conference and in a stunning display of organization that future generations would come to know as the "Revolt at Cincinnati," the rebel faction was able to decapitate and replace the entire leadership of the NRA with a single stroke. Out were the "elites," in were the "real people" who wouldn't hesitate to tell the government to get their stinkin' paws off their guns. Enter Harlon Carter, a former chief of U.S. Border Control (and murderer). Under his leadership, the NRA realigned from education to rough, tough lobbying, a mission which gave the organization's in-house lobbying group, the ILA (Institute for Legislative Action), a massive war chest and as much firepower as it needed.
The rest is history. In 1980, they handed their first presidential endorsement to Ronald Reagan, noted Second Amendment advocate and, um ... signatory to the Mulford Act. The 1980's also saw the NRA strengthen its ties with gun manufacturers by making them a boatload of money through helping to decriminalize and loosen restrictions on concealed-carry firearms, previously considered jokes (or "mouse calibers") by the wider gun community. The NRA hasn't done too badly with this arrangement either, especially given the $20-52.6 million and $2.9 million in donations and advertising dues (respectively) that they've received from gun manufacturers.
So are we suggesting that we retake the NRA for common-sense-wielding gun owners? Sure. But it's also important to note that they've opened a nasty can of worms that we're never going to be able to put back in the bottle. Basically, they've rewritten how we interpret the Second Amendment, and in doing so, made gun control an impossibility for the foreseeable future.
A well regulated Militia, being necessary to the security of a free State, the right of the people to keep and bear Arms, shall not be infringed.
Although it's easy to say that this very important phrase isn't definitive, people who don't ignore the historical context in which the Second Amendment was written -- people who actually stop and think about not only their rights but their responsibilities as parts of a whole nation -- know that it clearly refers to military activities, especially given the usage of the terms "militia" and "bear arms." It didn't need to be watertight when it was written because it was obvious to everyone what it meant. The Second Amendment guarantees state militias the right to bear arms. It's a reading that stuck with us from 1791 throughout most of the 20th century, and was even ratified by the Supreme Court on four occasions.