The problem is there are a whole lot of gun owners that don't have half a brain. And as for the 2nd Amendment protecting against tyranny, good luck with that argument. That was only loosely true when the Constitution was hatched and the idea pretty much died with the Civil War.
Only if you believe that the army would accept an order to launch nukes. Americans being armed still is a sufficient detterant from complete tyranny and subverting the will of the american prolle is an example of that which is what the fbi was doing.