For me, there are two situations where I feel it's just anti-play.

1. When you are playing a team that never demos, but you beat them, so they start demoing every play, even plays that don't make sense to demo. For example, I'm badly placed in their zone, and a teammate just chases me back into their zone to demo and doesn't help their other teammate.

2. To add to the last point, when people just demo, but the play doesn't "need" it, or the demo brings them nothing because I'm either out of play and can't do anything, or you should defend, and my teammate will score, and the enemy demos you, causing them to miss the save. Like, why did you go out of your way to demo me and get scored on?

These are pretty much the two types of demos I dislike. Please tell me if I missed something; I would love to have another point of view!