Did the NRA ever call for the banning of the Bump Stock? All I saw was the suggestion that the BATF should review it's findings about it's legality. But I may have missed a later position by the NRA.
If they did not, then perhaps the NRA's suggestion was made knowing the BATF would not likely be able to reverse a determination that follows the laws and specifications in place.
Also, the NRA suggestion "trumped" any of the Antis using the NRA as the bad guy.....as has been seen, their supports tend to get emotional about Who is doing something rather than What they are doing...like they support legislation they are told is Bernie's but oppose it when they find it is Trump's...