Perhaps I misunderstood the intent of your original post. For some reason, you seem to want to equate the responsibilities of gun manufacturers to those of bartenders.
My point (and yes, I do have one) is that their respective proximities to their customers is quite different.
A gun manufacturer sells through distributors to dealers to their customers. A distiller, likewise, sells through distributors to businesses then through the bartender to the final customer.
The gun manufacturer doesn't (and can't) know who the final customer will be; same for the distiller. The bartender, on the other hand, is standing right there filling his glass. AFAIK, in most (if not all) states, it's illegal to continue serving alcohol to obviously-drunk customers.