Laws are never made for the responsible majority, they are generally made to protect the responsible majority.
There is no doubt a responsible gun owners can have an AR-15 semi-automatic military grade assault rifle and never do anyone any harm, the question society has to ask is, is it worth...
Is there any particular reason not to deal with both at the same time?
I'm not sure why civilians need to own a gun like the AR-15. A nice bolt action rifle with a nice wooden stock for some weekend hunting is surely sufficient.
Anyway, I googled your claim about 'plenty' of states have not...