Also, a proportional "party" in Paris would be two million people. Have fun controlling that.
Even if some rioting would've started, there would be no houses or shops to demolish, and it would be far easier to isolate the rioting core group from other people.
The mayor refuted such plans with claims that that made the authorities responsible on the occasion something happened. As if that is worse than the current outcome.
In hindsight they should've blocked all access ways to the village (train and roads). I say in hindsight because people simply didn't expect this to go so wrong.
The lesson to me is that mobs are a scary thing. They can turn angry very suddenly as people start to copy the behavior of the first person to throw a stone.
It seems that the authorities where too ambivalent. On the one hand they said please don't come there's no party, on the other hand they prepared a football field for people to go to (without music though). They should've stuck with the former and enforced it by not letting the trains stop in the village and putting up road blocks.
Hindsight says that they should have made it hard to take the train there.
I sort of think the problem will mostly go away on its own, most people aren't going to want to repeatedly act as human shields for hooligans.
Sounds kinda pointless because people can use the GPS on their phones & maps to get to the correct place, signs or no signs.
One disadvantage to that is that the pitch could be ruined then. Thousands (or hundreds) of people on a grass field and it'll be mud city. What happens afterwards when that pitch is supposed to be used? Who pays (potentially) for reseeding it?
Two years ago similar problems where arising in France, called Apéro géant. The crowds intended to organize the biggest party at the Eiffel Tower, everyone feared problems. Authorities sealed the surroundings, but let everyone pass through as long as they handed in their alcohol. Once arrived at the location there was not much of a party so nothing happened.
It's going to be interesting to see what happens to social media monitoring, also interested to see what happens with the damages and the people on tape (youtube, fb et all)