That might be a good argument in theory, if it wasn't for the part where US police don't have to protect citizens and all the population that are outside of effective police coverage. It's not the argument gun control campaigners seem to be making right now. They mainly seem to have gone for the approach of supporting police officers standing by and doing nothing as kids are murdered one by one. Given that, I suspect you're going to have a hard time convincing people who don't already agree with you that they should give up their guns and let the police take care of everything.