It doesn't matter how you and I interpret constitutional language, but the US courts. They routinely limit plainly-stated rights. For example, there are laws concerning slander and defamation which apply to the press despite a specific "shall make no law abridging free speech of the press" prohibition. This is arguably even stronger language than "shall not be infringed", but the legal weight of such distinctions is zero.Well, how many ways can you interpret "Shall not be infringed"?
If you face government reprisal for exercising your right to do something, you don't have a unrestricted right at all. This is not technical freedom; the government can and will act to punish you with perfect confidence that courts will not find your rights to be infringed later.The constitution doesn't award these rights to anyone, it guarantees them to everyone, they are inalienable. And technically under the 1st Amendment you are free to threaten anyone, however it doesn't protect you from consequences of how you exercise that right.
You are right that the NRA aren't a fringe group on face value. They had revenues of $440m USD (circa 550 AUD). However, they do pursue many policies with minimal broad support (for example against background checks, supported by circa 90% of Americans), often out of fear that they will be outflanked by more extreme groups if they don't resist everything. They are an outstanding example of the effectiveness of well-funded single-issue groups vs the wishes of the American people. You see many, many other examples in areas like tax, industry regulation, military etc.The NRA aren't a fringe group, and compared to the high rollers in the anti-gun lobby, they're relatively under funded. They are a lobbying group for the members and draw their money from membership fees of the people they represent. I think people seriously underestimate how widespread gun ownership is, and that they're largely held by people who aren't the typical "flannel wearing hick sprouting off about my rights" type of person, but fairly normal people who just happen to own guns. They're a successful organisation because they adequately represent their members, and they're given power due to their public support.