Well, the idea is that no one would actually wear body armor unless they expected to be in a situation where they would need it, and the only such plausible situations are extraordinarily likely to be criminal.

However, I tend to agree, in that there are legitimate uses for body armor outside armed robbery and expected police shootouts, peace of mind in northern Virginia these days being one of them, hunting accidents being another, and I have major problems with laws that attempt to reinforce already-illegal acts by making illegal acts that might lead to them that also make illegal the same acts that wouldn't lead to illegality.

This one, in particular, I'm a little iffy about, because I can't imagine anyone actually using body armor in relation to non-illegal acts; I don't think that there are very many hunters out there that would wear body armor if it were available to them (not that I have a consensus on this), and I doubt that your average citizen would be willing to spend a thousand dollars to buy one for each member of the family when it's easier to just stay home.

In addition, I seem to have overstated it a little. It would appear that in many states it's illegal for felons to purchase body armor. In some states, it is illegal to purchase it at all. I believe that that is more accurate than my earlier statement.