Remember they nominally support background checks...
I mean seriously, these guys don't actually give a crap about gun owners. The only people they actually strive to defend are gun sellers - and they want to make sure they are able to sell to any criminal.
So far as I've read, the deal also closes the gun show loophole, which I'm sure is what the NRA can't stand, and is also the best thing in this half-baby step. The NRA doesn't care about how many dead kids we have, so long as we keep selling more, more, more guns.