Well, after visited Sebring this year, one can only say I'm very glad the French police are not as irritating as their American colleagues 
There is plenty of behaviour that they allow that under normal circumstances could not normally be tollerated - I am not just thinking about the type of behaviour I alluded to earlier but all sorts of things including various traffic and public order offences.
Bad behaviour at LM is nothing new. Mike Hawthorn himself got a girl pregnant at an after-race party and he never visited the kid.
The worst times were actually in the late 80's when the "Our Nige" fanclub (Mansell) used to visit. The punch-ups with the Germans in the Village Bierkeller were legendary, together with pig ignorance and the abuse of gate staff, bar workers, police and anyone else who got in the way.
The problem these days is a bit different, but to think it's restricted to the British is not correct. We probably show up on the radar more due to being the majority of fans. Whilst this doesn't make me proud, it certainly won't stop me flying the Union Jack either, to do so would be cowardice. Oh and the Commer will never fly the EU flag. Never I tell you.
Turning to your comment above, to be honest, I'm not sure the police actually "allow" it to go on, it's more a question of being unable to prevent it due to lack of resources. The area to patrol is so huge of course.
Having said that, I think Les Flics could spend their time far more productively by clamping down on the sometimes disgusting and dangerous behaviour of a minority of fans, at Houx Annex roundabout for example. Instead we see dozens of the useless jackbooted kepee-wearing knaves setting up yet more speed traps on the Mulsanne straight, strutting around, throwing their weight about and pretending to be big men by trying to catch folk exeeding 65mph, or horrror of horrors, spinning up their back wheels. Like police all over the world, the US included, Les Vaches see the motorist as an easy target. Le mans must prove to be an irrestistable opportunity to be fleece us to pay for their Xmas party.