People that play on deserve to be stripped of all material but their king, then watch helplessly while the opponent promotes every pawn they have to knights, then get mated by a herd of horses in the most humiliating manner possible...that's how you teach people to resign.
Don't respect that I have the skill to beat you in a clearly won position? Then I won't respect your ability or time either. Believe me, after I mate you in funny patterns a dozen times in long drawn-out frustrating games, you'll learn to resign. If you are obstinate, I'll push your king around the board for hundreds of moves forcing you to spell out "I suck at chess and do not know when to resign" with your king...
P.S. I am a nice player. I reserve this kind of lesson for people that are so stubborn about not resigning that they won't resign in a K+Q vs. K or K+2R vs. K situation. If you opponent is kicking your a$$, and you know how to win the game from their position, then guess what? They know how to win the game from that position.
Fight on to the Bitter End?