Simon: "I can't believe anyone ever opposes such a thing."
This might seem hard to believe, given the present state of things, but there was a time, back in the 1980s, when the NRA was in favor of a background check. The situation was this, Liberals wanted a traditional background check - which in those days involved bureaucrats and filing cabinets - but the NRA wanted a computerized background check which involved computers which were relatively recent technology.
The Liberal media actually opposed the computerized background check because they said it was too expensive. Back then computers up to the task would have had some expense but not enough to justify the Liberal position, especially in contrast to an archaic bureaucracy with paper records.
I know this because I was there witnessing the issue unfold from both perspectives.