Wow, there are poor sports in OTB play as well as the internet? As HgMan said, "Who knew?"
I try to be stoical and sympathetic to the poor sods who don't know any better than to play on.
and on,
and on.
I get much more frustrated with myself when I make a hash of a game in an early round and either win inspite of myself or give up points that I considered mine.
I did have an interesting learning experience recently. I went over a game in which my opponent offered a draw when I had a Bishop and 4 pawns vs 6 pawns. I simply thought that the other player was getting frustrated because I'd put him in zugzwang and then start moving my bishop back and forth. It wasn't the most imaginative win, but it was obvious to me.
I only realised later that my opponent probably really thought the position was drawn and made the offer because he didn't see that I was making progress. That was a lightning blast of enlightenment for me. I've since used that and similar positions to teach my students how to win won endgames. So, playing weaker opponents can sometimes be very educational.
Also, I'd rather face a refutation to one of my opening lines against a weak opponent, have a chance to save a point,
and learn a lesson than to have that same refutation occur in a game against someone who will then put me out of my misery for my mistake.