Bananacorner
SILVER ELITE
As parent of a GK, I've often violated this "rule" to be closer to my daughter, especially if filming her (some leagues mandate parents all on the same sideline, but segregated by the half-way line). Whenever I do this, I always keep my mouth shut, NEVER say a word, not even to cheer a goal or save. Most of the other parents can tell that I'm from the other team, but have never given me a hard time or commented on my presence. Sometimes, I'll even say to the closest parent, "Hi, I'm the GK's dad, I just want to film here, and I promise I won't cause any trouble." That always breaks the ice and things are very polite and friendly from there on. Furthermore, if someone did give me a hard time, I'd simply go back to my team's spot without a word, because I know the rule. Still, it it is a good way to make you keep your trap shut. I noticed it often also has the same effect on the other team's parents, where they will be noticeably inclined to be more polite because I'm there. The rule is there of course because it is easy to get into verbal back and forth with the other team's parents. All it takes is for one person to yell "Foul!" and the other parent to go, "No, it wasn't," and things can get ugly quickly. So if you don't have any self-control, definitely stay on your team's end.
I must admit, when a parent had quietly edged up behind me to watch the game (I didn't turn around to see who it was, just felt his presence), and I realized from him suddenly shouting "that was a foul!" against our team that he was a parent from the other side, it took restraint to keep from standing up quickly to "accidentally" head butt him. I think until you are 100% certain that you can control yourself, standing next to parents from the other team is a dangerous way to try and keep quiet...