My father owned a few guns. When I was a young teenager, I went out shooting a number of times with him and my brother. It was fun. We stopped sometime after my Dad started developing health problems.
I didn't pick up a gun for years. Recently got my interest rekindled. In the meantime.... I wouldn't say I was an "anti" but I was certainly more pro-gun control.
It makes sense to me that there are antis. If a person doesn't shoot, and isn't interested in guns at all.... the main perspective many people get drilled into their heads is the harm that guns do. They just see guns as tools for criminals. They seem them as threats.
Give that same person a gun and teach them to shoot, and they might learn how fun shooting can be, and gain the confidence that they could use one to defend themselves.