The issue with this argument, for anyone who comes after, is not when you give a gun to a SINGLE person, and then ask them "would you do a bad thing".

The issue is when you give EVERYONE guns, and then are surprised when enough people do bad things with them, to create externalities for everyone else.

There is some sort of trip up when personal responsibility, and society wide behaviors, intersect. Sure most people will be reasonable, but the issue is often the cost of the number of irresponsible or outright bad actors.