I have been playing tennis for quite a while and truly believe that this sport picks up some of the strangest people that don't play well with others. In other team sports, this type of behavior is just not accepted.
In terms of delusion, I think the worst subset is between the 4.0 and low 4.5 level in tennis. This is the level where people can have good rally's sometimes when their opponent hits it hard at shoulder level with moderate topspin (not too much of course). Even with this most guys miss before the 7th ball. I believe this is where the distaste for pushers comes into play, as well as the sand baggers. They are looking for the just right opponent. Someone they can bang the ball with and be close or win.
I have improved recently to the point where I am beating people at this level easily, and have been quite unhappy with the behavior. Its funny when someone who loses 6-0,6-0 attributes it to a bad day. Sadly there are other much less pleasant ways people have dealt with loss.