There is no "undecided middle" anymore. Hasn't been for years now. Everyone has already picked a side. The people who are for gun control aren't going to change their minds and the people against it also aren't going to change their minds. Even if there was, they don't have any need to "convince" people to be pro-gun control. They can do whatever the fuck they want no matter how unpopular. If they wanted to enact a total ban on all guns tomorrow, no one could do anything immediate to stop them from doing it. The only avenue to challenge it would be to go to court with someone who didn't turn in their guns as a plaintiff (who would be in jail), then wait 5-10 years for the appeals process to reach the SCOTUS, assuming that they bothered to take the case in the first place, which is unlikely. By then it would be effectively moot since everyone would have either turned in their guns or (more likely) buried them.