The USAF believes it has a "divine right" to own all land-based fixed-wing aviation, and has always resented that the USMC has its own fighters and tactical transports.
Nothing new there then! Precisely the behaviour of the RAF over the past few years and copied by the FAF in trying to take over Aeronavale. The difference is in the fact that the USMC is the senior service in the US and has the greatest political lobby base.