No argument is an effective argument against someone that forgoes reason. You can really only ever hope to persuade those that think more critically, in any argument.
In either case, I think that willfully improper use of a firearm in blatant disregard for the safety of innocent people around you is clearly and directly comparable to willfully improper use of a phone in blatant disregard for the safety of innocent people around you. "False equivalence" seems to be a buzzword these days for anyone presented with a comparison that they don't like, weather it's actually "false" or not. Those people need to be called out when they do that.
If it doesn't convince, then an argument like that will hopefully at least frustrate someone that refuses to think rationally into instead reacting emotionally to it, in turn exposing their opinion for what it really is: an ill-conceived and emotional reaction, not a thoughtful and realistic stance.