After spending years trying to convince people that the problem is the criminal and not the weapon, it became clear that there is little that can be said.
Where the fear of guns is entrenched you have no chance of changing anyone's mind. It isn't going to happen. Accept that. It is possible to sow some seeds. To encourage people to think, and to perhaps use one of the previously listed arguments to lead to a question.
But if you don't accept how hard it is for people to question their deeply held belief systems the argument will bring nothing but bad feelings and frustration.
My advise, should you wish to use any specific arguments or tactics is to speak kindly, speak softly and retreat to silence quickly.
Asking the person if they really want to hear your response before you answer can help open their mind.
If you get the golden opportunity to really open someones eyes please PROTECT THEIR EGO. Let them save face, and give all respect due to someone who has taken the tremendous step of changing their mind on something that is core to how they see the world. It is rare, painful, difficult and amazing thing that they have achieved.
Fear of guns is as deep as any religious or political belief.