It's as simple as this: There are people out there that just can't STAND others having something they can't have or do not want for whatever reason. So, these people, who don't want to own any guns themselves, simply don't want others to have them.
There really is no other way to put this. These same people, if they couldn't have a black car, or simply don't want one, wouldn't want you to have one either. And, they would come up with all sorts of crazy half-cocked reasons why black cars are "evil". In fact, California had passed a law against black cars some years back.
The bottom line is that there are ignorant people, jealous people and stupid people in this world. Gun banners are all that rolled up into one. You really don't want to pander or appease these types of people. It's like pandering to or appeasing Momar Khadafi.