Police shooting the unarmed won't change if citizens aren't allowed to own guns, so that really shouldn't weigh on the statistics. People do misinterpret threats, and obviously if they weren't allowed to own guns that number would decrease dramatically, but I'm wondering how big a problem it actually is now; do you have any statistics that show that this is anything other than a minor risk? As far as depressed people committing suicide, I find that to be an incredibly uncompelling case for banning guns. Since when does protection of depressed people trump the rights of others? If we cared about depressed people, we should ramp up the war on drugs and reinstate prohibition of alcohol, as these are frequently abused by the depressed; are you in favor of those measures?
"No, sorry, you can't hunt anymore, some guy's wife just left him and we're pretty worried about his mental state."
"Couldn't you just not sell guns to him?"
"Nah, it's easier to just take them away from everybody."