Nobody needs a Hummer, a TV, a computer, Big Macs, breast implants, Democrats, easy bake ovens, reality TV ....
Geez, who in Government decides what we need? Can I have that job!?
The Bill of Rights was written so that people would not need to fear their own government. A government that fears and respects its own citizens does not run roughshod over their rights.
Exotic and highly destructive weapons could be restricted or banned, because no one needs a machine gun or grenade launcher for protection against ordinary crime.I'm perfectly comfortable with laws forbidding the carry of weapons for self-defense that cannot be used without endangering innocent bystanders.
I'm perfectly comfortable with laws restricting the use of these exotic and highly destructive weapons to places and times where they pose no threat to anyone.
If you want a Mk 19 full-auto 40mm grenade launcher, I've no real beef with that. But I do think it reasonable to require that you only use it on a properly-managed range. (Grenades sometimes fail to explode, so it's not just a matter of making sure that there isn't anyone in the line of fire, but also that you're firing in a place where unexploded ordinance can be either safely left, or properly disposed of.)