Regarding semi-autos, I ask if people should be allowed to own sports cars capable of exceeding the speed limit. Of course. Most behave responsibly. Yet there are 40,000+ traffic deaths every year. And the right to own a car isn't specifically enumerated in the Bill of Rights.

Regarding guns in the house: I ask them if swimming pools should be banned. I then point out that even anti-gun researchers have conceded that you are 100 times more likely to have a kid die in a drowning accident than in a shooting accident. I also point out that those numbers are skewed by guns laying about in the homes of gang bangers and meth houses - People who are illegal possessors anyhow and would have guns even if they were blanketly illegal. I point out that this is happening in the UK where guns are banned but come in with the drugs. I ask them if they lock up their car keys when they come home. Huh? Well, aren't cars just as capable of killing? Aren't you worried about your 8 yr old kid taking your keys in the middle of the night and joy riding? Then why are you so concerned with a gun in the house?