I would like to know the principal's motive. There's got to be more to his story--why did he cave so easily? Has he mishandled "scandals" in the past? Something doesn't add up.
This type of celebration is prevalent in boys' soccer--I personally see it pretty often, from young-age select soccer all the way to the professionals. (and believe me, I watch a TON of soccer, with two daughters playing select) I think I'm more ticked over the other teams' parents--get over it, your team lost. Sorry--don't call and complain after the game. Geez...