I don't think involved is the word you are looking for, obsessed with winning is more like it.
I coached Little league baseball for 9 years, Popwarner for 4 years, and was a leader in 4-H for 8 years. I never had a problem with a the kids, we may have had some issues (13 year olds in baseball) but they got worked out quickly. The parents are the ones you have got to worry about, I would draft my baseball team with the parents being part of the criteria, if I new knew the parent was a pain, the player would slip down in the draft as far as I was concerned, not that i didn't like the kid or want them on the team, I was just not looking for the head ache that came with the parent.
I would rather have parents want to be involved, than some of the other type. The parent that just drops their kid off ask, what time practice or the game is over, and just shows up at that time to get their kid, I think that is allot worse than an over zealous parent.