If you are going to respond, at least address their point ... which is not traditional, interstate sales. What they are squawking about is Internet services that facilitate face-to-face sales, that CAN be consummated without benefit of FFL or background check.
Of course, in the case they chose to highlight, the seller KNEW he was selling to a prohibited person and went ahead anyway, so any discussion of background check would be moot in this case. The illegal buyer and the illegal seller have both been prosecuted, so the law works.
No matter how mandatory the 'gov makes background checks, they are never going to get the drug dealers in da 'hood to call NICS when exchanging guns for drugs (or drugs for guns).