So does these situations pass your sense of ethics?: I book a mandatory two night stay on-line with Marriott after which I then call Mariott who drops one night at my request. Or, I see a two night minimum on-line, don't book it, but then call Marriott who books a one night stay for me.

Give your weak kneed situational ethics a rest. Only Marriott can give you a reservation and only Marriott can undo or change a reservation. So long as you are not deceitful or lie, which is always wrong no matter the situation, then you have done nothing wrong.