Look them squarely in the eye, tell them,
"You know someday you may need this stuff, or you wouldn't be asking if you could buy from me. The time to arm yourself and stock ammo and other supplies is now while you can get it easily and cheaply. When the day comes that you really, really need it you won't be able to buy it for any amount of money, and I'll tell you no. I tell you this now as a friend. You can choose to act on it, or not. Should you decide to prepare now, I'll be glad to advise you on what firearms to buy, the magazines, spare parts, ammo, and other gear you should have. I'll teach you to shoot and maintain your gear. But I won't be your warehouse. So, like life insurance, homeowner's insurance, car insurance, this is freedom insurance. You must decide if you love your family enough to prepare for their safety."