It would explain short term resistance maybe.
It does not explain at least 10 years of over 50% approval in both parties for private sale background checks. Gun control advocates even state that most gun owners support private sale checks, a claim I suspect may be true.
We may even get a bill approved at some point. If so look for it to have a sunset clause of 10 years just like the federal assault weapons ban had. This will be portrayed by gun control orgainizations as a NRA requirement. The NRA will take the credit but wouldn't have required it.
Like the assault weapons bans, cases will wind their way through the courts arriving just in time for the 10 year sunset. If the cases are believed to be successful gun control will allow the law to sunset so as to not have a SCOTUS ruling in hopes of resurrection at a later date...exactly like the federal assault weapons ban. If the cases are projected to fail, gun control will lobby and campaign loudly to not allow the law to sunset.
I don't hate or even dislike gun control advocates. I do dislike people who tell demonstrable lies and pretend others are crazy when they point out the truth. Now the commerce clause theory is just that, there isn't any better, reasonable, or believable theory I have heard.
I would support background checks on private sales in my state if the feds enabled use of NICS so my state didn't have to reinvent the wheel to provide background checks at tremendous duplicate cost.