Membership dues provide less than half of the NRA's funding - a very large amount (tens of millions) come through sales of guns. How various organizations under the umbrella of the NRA get funded
So the NRA at least has a financial interest in the success of the gun manufacturing industry.
The quid-pro-quo for the gun manufacturing industry came when the NRA pushed and got passed legal immunity for liability related to the use of the gun industry's products, even in the case of defective and unsafe products. This was unprecedented. Manufacturers of defective or unsafe weapons now enjoy legal protection that Ford never received when manufacturing the Pinto.
The NRA does not act solely as a gun-manufacturers rights organization, but it is both significantly funded by gun manufacturers and has acted to protect the financial interests of the gun manufacturers. It is not "outrageous" to point this out.