I would add that there is similarly no justification to limit the protection to arms that have "legitimate civilian uses".When I consider the list of what I consider "legitimate civilian uses", and try to envision a firearm that would not be appropriate for any of them, I come up empty.
What firearm would you consider to not have a legitimate civilian use?
I wouldn't consider any to not have such uses, and that includes arms beyond just "firearms". However the anti arms rights crowd is always blathering about how this or that arm has no legitimate civilian purpose. (Too big, too small, too ugly). Thus the fact that the amendement provides no support for any such restriction is important.