I voted yes, but not in all situations.
If I'm playing a 1 on 1 money match and I respect my opponent ability and character, then yes I will. If my opponent doesn't do the same, then I would readjust. This is usually not the case.
If I'm playing some a**hole, then no I won't. No matter how good or bad of a shot he is. You usually get a good idea even before the match begins.
When playing a team match, I usually won't. The reason is because I have a personal responsibility to my teammates to uphold. I not saying I never have or my teammates never have, but this is just a general rule of mine. I would normally defer to the team captain if there was ever a complaint. Generally, it is not spoken about and it wouldn't matter either way with my teammates.
The bottom line is if you cant concede a game or two, your probably out matched and will lose anyway.
Be a good sport and offer the olive branch when the situation is right. Besides, if it really matters, it is probably about money and you want to get away with the money without a confrontation. This will go along way for your karma.
I dont believe in being petty about things like this.