I know some grown men who at times can pretty childish on the court. I've seen a number of them who have just stopped the match because they start shouting at eachother. Recently, on two occasions two different player 'lost it' because they claimed the guy returning their serve was making calls after he'd hit the ball. (I played this returner later and understood the frustration) However if a guy has a big serve how quickly do you have to call it out? The other big source of fights is calling a serve out and then chaning it to good. Some guys wanna take two and some guys want the point....Silly stuff.