This is a touchy subject. There is a fine line with playing aggressive and going to far. There is also the matter of parents cheering on the kids and being belligerent. First and foremst, kids should have fun playing sport (or any other recreation for that matter). Some kids enjoyment can range from playing in a non-competitive sport, all the way up to traveling team sports.
This should be the number 1 priority of parents at all times, no matter what activity it is. I understand some activities can hit the pocket book pretty hard. Some examples are hockey, dance, ice skating, football. Even sports such as basketball, soccer, and baseball can be a money suck.
Allowing your children to participate in such sports is great, and I applaud every parent who are able to support their children in their interests. With that being said, just remember that it is YOUR choice to take on this financial burden, not the child’s.