This is hardly a new point. Those of us who opposed what US imperialism was doing in Vietnam pointed out exactly what you just did, 40 years ago. I wrote a leaflet about the effects of those weapons (info from SIPRI, I think) and distributed it to disrupt military recruitment events in Edinburgh a few years later.

The British government moaned and whined loudly when the IRA got hold of a few Armalites. Dishing it out and taking it are apparently governed by different moral rules. According to bourgeois morality anyway.