Supporters of the 2nd Amendment will turn this into a debate about the rights of gun owners over US citizens right to life.
But that's a false narrative. Reasonable people will accept that rocket propelled grenades and other weaponry more destructive than guns should not be for sale at Walmart.
From there it shouldn't be hard to define a line over which certain kinds of guns should not be in the hands of your neighbors. They need to ban the sale of guns that have no civilian purpose. Any other excuse is just a pretext to lead the argument away from the facts.