Go look at the package on a kitchen knife and it says not to be used as a weapon
I'm not sure this is still a useful analogy, though...
The knife manufacturer isn't obligated to sell to you in either case, I'd expect them not to cut ties with you in the self defence scenario. But it is their choice.
Also, in the cases you can't, it's generally the government stopping you, not the gun companies.
Edit: hell I get downvoted and look where the knife analogy got us. A load of weird replies miles away from anything related to AI or DoD.