What would happen if everyone who wanted to recreate on this beach simply ignored his signs, took down the gate, and treated the road like the public right of way it should be? The police already declined to press charges on one group of surfers who "trespassed" right?

Ultimately, he doesn't have the power to physically prevent people from going to the beach, and if enough people ignored his buffoonery the state would probably not consider it a useful expenditure of policing resources to enforce it.