I put myself in his shoes (then again, I'm a 46 year old middle-upper class white guy that has never owned a gun)...
I'm catching a ride out with one of my friends on Friday as we're going to watch games in Philly...I often carry a gun, but leave the gun in his car as he heads out to dinner, and he drops me off at the bar I'll be at on South Street. I text him and say "there are a couple shady characters hanging around here, please make sure to let me know when you're here as I'd like to have my gun on me in case something gets crazy tonight". I go grab it from him...then, something goes down, I give the gun to my friend, he ends up trading gunfire with a guy, and someone in the other party dies.
Horrible situation all around. But, do you really find the initial guy at fault that returned my own gun to me, especially when I'm not even the one that fired it? Do you think the right move if your friend asks for his gun back because he feels like he needs it would be to ignore him or refuse to return it...and if you did, how would you feel if anything bad ended up happening to him that night and he didn't have it for protection when he asked for it?
I have little connection to the "gun culture", but if I did, I can't imagine not returning a gun to my friend that is it's rightful owner if he was in a situation where he felt that he needed it back.