When a beginner is continuing to play new captives into my territory, is it more considerate to keep passing when I can, or to hasten the opponent's understanding of the position by capturing promptly? (I can afford the extra points I'd lose by playing in my own territory.)

I'll give You my opinion as a beginner.

When this happens, please explain that it's hopless, and/or how it is that way. That way, at least I would be very happy, cause it increases my understanding of the game.

And I would be happy to “Pass for counting”, when I see it's over.

My view is:

beat your opponent as hard as you can.

Then explain, if the opponent is willing to hear only, what went wrong. The game is lost anyway, so it really doesn't matter by “how much” you win.

I've come across people who simply don't want to hear any advice at all, and just keep on playing weakly. It is their right to do so.

This is only my opinion, of course