A comprehensive list:

• You care entirely too much about the outcome of a game between 7-9 year olds (or 10 or 11 or 12 or…) and yell at the kids. On either team. Not cheer, yell.
• You yell at the refs.

That’s pretty much it. I personally could do without the cowbells and cheering for goal number 10, but whatever. The kids like it and I guess technically that’s supportive. Yelling “That went in!!!” as some 8 year olds sloppily handle the puck and score on their own goalie isn’t. Newsflash sir: your kid isn’t going to make it to the NHL. I think I would know, because mine definitely are.