I am rather pressed for imagining when a Stinger becomes a 'self-defense' weapon for a private individual, outside of an armed merchant vessel and it's crew.
Well, there's one example right there. I'd also say self defense against the government would also qualify. The difference between nukes and stingers is that yes, both can be abused, but a nuke can't be
used without being an abuse. You
will end up harming third parties with it, no matter what.
Obviously, there's some dangers with legalizing everything, and I wouldn't be against localizing control of heavy weapons instead (stingers and the like), so that each town had a store house of what people wanted to have just in case. In a worst case scenario, one is able to raid the local storehouse if necessary. This, along with a Defend the guard type bill that re-centered local control of the National Guard, would be huge steps forward.