When I point out universal background checks requires universal registration to be even partly effective among the portion of gun owners (law-abiding0 who aren’t a threat anyway I always follow up by pointing out that universal registration of just rifles failed due to civil disobedience in -Canada-! The anti-gun rights folks favorite example of a gun-free paradise.
Canada has fewer gun owners, fewer guns, no 2nd Amendment to “cling to”, and a culture that is not noted for being rebellious.
I note that fact, as well as the fact that their registry never had anywhere near full participation and was shelved after costing millions and not contributing to the solving of even one crime.
I usually folow-up by pointing out that their handgun registry did have more complete participation but also cost millions for zero crimes solved.
These are incontrovertible facts and undercut the anti-gunners claims about registries, and thus background checks, when explained to the undecided middle who we need on our side but who want, and deserve, more than a “It’s my right so fuck you”-level argument.