Seems like the military had problems in Okinawa since forever. Why not just restrict the military to the base and ban them from interacting with the locals?
Until recently, the Japanese had only "Self-Defense Forces." Everyone in the region has reason to fear China .
Americans do pump money into the Okinawan economy. Servicemembers are not a big part of the economy of Mainland Japan. The bases tend to be adjacent to larger cities. One Marine base is managed by the Japanese. It does bring money into the economy, but they would easily survive economically without the base.