It can't be done.
You will never convince an irrational person with rational thought.
It's easier to send the irrational person into complete meltdown by agreeing with their position but doing it in what they perceive is an “irrational” manner.
When someone starts with the gun control simply agree with their position and tell them democrats have been trying to tell people since the end of the Civil War freed slaves shouldn't be allowed to own guns.
As they are then busy trying to defend themselves against being a racist they will then claim no one should own a gun.
Again agree with their position and tell them how great it worked in Nazi Germany.
Considering the left responds better to short sound bites and visual than long winded mental, it's time to put out posters with visual of gun control at work.
Pictures of lynched blacks with GUN CONTRO WORKS.
Pictures of concentration camp Jews with GUN CONTROL WORKS.
It's time for the left to go on the defense.