I draw a dark line of distinction between f'ing with my pay/compensation (let's not get into the "allowance" vs "pay" dick dance - it's income), and co-location.
You are still missing the point. Your CO can literally order you into government quarters and you will lose 100% of your BAH. BAH, as published by the DOD, is to cover the cost of housing on the private market (for you AND/OR your family), but isn't required to be paid if you can live at cost to the government.
I'm not an idiot and I fully understand that the vast majority of military people live out and town and consider their pay to include BAH as their total compensation.
However, if the military says that they are now only going to pay one military member BAH in a mil-mil couple, they are still providing the required compensation to house the mil-mil family. They could also order that mil-mil couple into government quarters and they now lose both BAHs. When I'm saying quarters, I'm not talking privatized housing, I'm saying on base in a barracks/Q style living.
The compensation package is to have housing costs paid for. The military isn't the civilian world so if the military says that the total compensation package of a mil-mil couple should only include one BAH payment, it makes fiscal sense.
That said, I'm not arguing that dual mil folks are getting overpaid or taking advantage of the system, I'd never fault someone for getting a good deal. However, one can only expect a good deal to go on for so long and shouldn't be surprised if that good deal changes.