Any gun owner is law abiding right up to the point he shoots someone in the face. Law abiding has absolutely nothing to do with it. Can't you think for yourself what is good vs. bad instead of referring to laws?
This argument can be used against anything: Any man is law abiding until the point he starts beating his wife. Therefore we should have surveillance cameras in all houses...
Also, the Supreme Court, 9 to 0, agreed that the dependent clause was irrelevant, and that the "individual" vs. "collective" interpretation was correct. They of course disagreed on what rights it confers, but the collective interpretation is as dead as can be (a terrible outcome from the millions of dollars the Joyce Foundation invested into trying to establish it).