It's a good idea. Our German neighbors recently sentenced the father of a kid that ran amok with his gun which he didn't lock up properly.
And of course you can draw a clear line. It's all about the purpose. Cars are for transportation. Kitchen knifes are for cutting food. Chain saws are for cutting trees. Guns are for killing
There should be major restrictions for buying weapons. And if after a crime the gun can be traced back to an arms dealer who didn't make sure to check the buyer thoroughly and to follow the laws, then the dealer should get punished as well.