A Democrat from California has a brilliant idea: let's make sure citizens are easy to kill.
We must be suspicious of a government that is constantly on the hunt for ways to make us easier to subjugate. The fact that one could use body armor to enable criminal behavior is no more telling than that one could use firearms to do so. All the same arguments apply, but in addition there are several others that apply to armor specifically.
The 2nd Amendment speaks of a right to keep and bear "arms" that shall not be infringed. "Arms" as understood in the 18th century plausibly includes armor, though: Blackstone defines a gentleman as one 'one qui arma gerit,' but he means heraldic arms, which are the symbolic representation of a real right to bear armor onto the field. When Blackstone speaks of the natural law right to keep and bear arms, he follows contemporary English practice of limiting the right as "suitable to their condition." Any free Englishman had the right to certain weapons, but not just any weapons: gentlemen were "suitable" for better arms than yeomen.
The American ideal is that the Revolution 'gentled the condition' of all Americans. We are no longer supposed to have separate classes with differential access to rights 'as suitable for their condition.'
In addition, armor is purely defensive in character. Wearing armor by itself does nothing to make you more dangerous to others. Imagine that Schlock Mercenary-style armor were available that could, instantly, make you safe from bullets. Would that not be a plausible answer to school shootings that we'd all want for our children? In principle, then, we ought to agree to defend the right to armor -- and work to improve it, until it is as good as we wish it were.
Is not protection of one's physical integrity a very obvious candidate for a natural right if anything is? Is it not, indeed, the basis for the natural law right of self defense that is so well-established in our tradition and so well-argued in the philosophy that underlies that tradition?
Of course it is. Say "No!" to 'body armor control.'