That might be nice, but unfortunately, the paper record is all they have to go on, as limited as it is. The record is fact. Opinions vary.
Seriously ... a national organization like NRA should not put its credibility on the line without good reason. There's absolutely no reason for them to issue an endorsement in every or any particular election. There are lots of good reasons for them NOT to do so ... biggest one is that a poorly placed endorsement, like Manchin (for example) makes them look like complete idiots when it (predictably) blows up in their faces.
Don't try to defend the indefensible. Don't piss on my leg and tell me it's raining.
NRA should be ashamed of itself.