It’s not my job...

It's a crass analogy but it works really well:

Imagine for a moment that you're out in public and a strange gentleman you do not know urinates onto your legs.

Obviously, it helps that you are wearing pants at that moment, because it would definitely be worse if he were peeing onto your bare skin. But in that moment, don't you wish that he was the one wearing pants properly and keeping them on?

That's why it's your responsibility to wear a mask. You could be the one peeing on other people and not even know it.

How about you leave out the tortured analogies, and just speak plainly?

I don’t know you, and you don’t know me.

So, by what authority do you assign me this mask wearing “responsibility”?

Authority depends on your jurisdiction, but more generally - you just shouldn't be making people deathly sick. That's pretty much a rule every society of every kind in human history has agreed upon; it's up there with don't murder and no stealing. By authority of "don't be a dick to people".

I’m not sick, and have not been at all for years.

I reject your request I wear a mask to protect you from diseases I don’t have.

Unless you just took a test, you don't know that! It's highly infectious and you could be asymptomatic. There is no way you could know you're not giving it to people.

Yes, not wearing a mask is dumb. I'm glad you can understand that, Timber.

You are correct. It’s a really bad analogy.