Couldn't agree more. I played last year against a 16 year old girl who was lower ranked than me but played a very good game until she made a critical mistake. She then slowed the game down until finally stopping her moves altogether letting time run out instead of resigning. Afterward she sent me a request to play again, which I declined with an explanation that I preferred to play with people who displayed better sportsmanship.
I can't figure out why people have such a hard time losing. If a position is lost, make the best of it and then resign when it is clear that only a series of blunders by your opponent could change the outcome. It's just a game.
Reminds me of golf. I used to get ticked off when I played poorly. Then I remembered that I am a terrible player and should not expect to break 90 more than once a year. After that no more pressure. Same with chess. I am decent enough to play a good game, but am under no illusions about my current ability or potential for improvement. Small improvement possible, significant improvement at age 42 unlikely. So play, take your losses in stride, and don't be a dick. Good advice in chess and in life.
When deciding to accept / make a challenge to another player, I often look at their profile to find a bit more about them.
On 2 or 3 occasions I noticed pretty damming comments posted by a grieved opponent because the player hung on and/or slowed down play when he/she should have resigned or at least played at a decent rate.
While I accept that people play their moves at a rate that suits them and it is their prerogative to decide if and when they resign, should their ultimate demise be the likely outcome. But it irks when a player has a completely lost position but continues to play on, and to cap it they play at a slower rate than before (as has just happened to me).
I try to play my moves promptly, irrespective of my position, although I tend to focus on the more interesting games (usually one where I have the upper hand or good chances). The only thing that would slow me down is when I don't have an obvious reply and want to think and come back to the position - and often if that is the case I add a comment in the chat to say just that.
And if my position is a lost one then I will not delay resigning. Usually, when I do resign I thank my opponent and congratulate him/her.
I hope that does not make me into a goody-goody but I find the attraction of chess.com is not only I have a chance to play the game I love with people of like mind from anywhere in the world, but to see good sportsmanship in action!