We did not allow our boys to play with guns while growing up. I wouldn't do that now, but it made sense at the time. Little problem for them - boys just go "All right, swords and light-sabers it is, then" and move on.
Why would parents do this? If you follow the reasoning, there aren't many choices why. Sometimes I like to point out the obvious, simply because it is being consistently denied.
The parent must think that the mere ownership, the mere use of a toy gun, has the potential to make his child more violent.
There are many qualifiers here. The parent may think it is extremely unlikely to affect his own child, but there is a greater chance it will affect other children (that's a bit superior, isn't it?). The parent may think that the effect is small and most normal folks can master it, but a few can't. The explanation that this is less personal than cultural, an expression of being a good example of where society should go, a declaration that we shouldn't use violence to resolve our differences or whatever, is simply a dodge. That means exactly the same thing, one is just hiding from oneself with grand language. Other modifications may occur to you, but they all resolve to this point. Toy guns make you more violent.
One would think real guns would be even more likely to do that, correct?
So. Therefore, those who have guns are more violent, less moral, culturally inferior. Oh, maybe not you personally, but as a group, that must be how you are viewed. The other ways of putting this don't change that. To say that there are better ways to resolve differences, or that people in this society believe they need to resort to violence far more often than is necessary, is again an evasion from the base point. They think you are less moral.
Well, it may be all true. We might be able to show that there is some moral lack, or increase in violence, that results from ownership, possession, or even handling firearms. It's going to be hard to sort out because of selection bias, because there are three groups who buy guns: those who want to shoot someone, those who want to protect themselves, and those who have a gun hobby - hunting, target, collecting, re-enactment. That first category does include bad characters that we'd like to keep firearms, and lots of other stuff, away from.
Culturally, I'm not a gun person. My father's family were farmers and had guns and my mother's family were city people who worked in offices and didn't. My parents divorced and I grew up surrounded by the latter. I can't get my mind around wanting to own anything but basic home protection (not much needed in suburban NH). But my wanting and feelings and cultural preferences have nothing to do with the issue.
I'll write more, especially about the mental health angle, where I actually have some knowledge. But for now I just want the obvious stated. In this debate, the gun-rights people may think the gun-regulators are fools and interfering controllers. But the regulators, whether they recognise it or not, believe the gun-owners are less moral. How much less likely varies greatly. But it's there. There is no other way to get there.