True Marines (and soldiers, and sailors, and airmen) obey the lawful orders of their civilian superiors, as it should be.
The orders may be abnormally stupid or ill-conceived, but those orders must and shall be obeyed. Anything less is the path to a third world banana republic.
Would you obey an immoral order?
Don't agree. The dude could drop his papers and be on the beach sipping vodka tonics with full benefits if he wanted to. If he feels that homosexuality is not good for the Marine Corps then he should retire or fight it tooth and nail until drilled out of the service.