I shoot with a guy who's a former cop, and who now runs a shooting school. He wrote a great piece that focused on the "resisting tyranny" aspect of the argument, and when confronted with the "assault weapons are only for killing", his unapologetic response is, "Exactly, and that's why we need them!"
Another shooting buddy is a liberal high school teacher, and he is much less likely to be preaching to the choir when discussing gun control with friends and co-workers.
He warns that the resisting-tyranny argument holds no water with libs, as they think of the government as a benevolent nanny, so why would anyone oppose it?
His pragmatic argument is based more on the lack of justification for the government's restricting the ownership of something that has almost no impact on pursuit of life, liberty and happiness of anyone, whether they own the object or not.
Ask a lib if they'd spend cubic millions of dollars enforcing enforcing any law that addresses an object that is almost never used in crime? What reasonable response can they offer?