Either you wanted to be sarcastic or your simile did not work well.

That simile captures perfectly the logic here. I don't think it's technically sarcasm

EDIT: a better simile would be if guns were giving away for free. You can see how that could be construed as increasing the responsibility of the provider if a receiver then does something illegal with it

I really do not see that responsibility. It is so perplexing, so odd a perspective that some of you are advancing, that I could (jokingly, I understand good intention) call it resembling "gaslighting" from here - do you know, for example, in the series Parks and Recreation the topos of Ben not understanding why Li'l Sebastian would be a big deal?

I'll repeat a few of similes I used, with this latest: somebody giving guns away for free would be /less/ responsible if he screened the receivers first; somebody serving drinks would be /less/ responsible if he checked the costumers first; somebody in possess of a hammer would be /less/ responsible if he lent it to known vetted people instead of just anyone...

I get it that some see that cases for the opposite exist, but I would need a strong example because those provided made me strengthen the view I advanced instead of seeing an acquired responsibility on those who select their customers.

Don't get me wrong, I also don't see it personally. I just think that the framing is useful: it highlights how our society has a bias towards business and a bias against morality-driven initiatives

If selling the weapons is "ok" because business must be allowed because the motive is purely selfish (I just want to make a living for myself and my family), and giving away weapons is "suspect" because "you clearly have an ulterior motive", if just means that we live in a world where selfishness is the norm being altruists is suspect.

I think this is the core divide of our society, much more useful than the obsolete "left" and "right" divide

The metaphor is ridiculous and that's the point. GP is saying the GGP's argument is just as ridiculous