If one considers Kant's categorical imperative, "Act only according to that maxim whereby you can at the same time will that it should become a universal law," then also considers how they'd feel if they were go to visit a doctor who had cheated or is cheating, one certainly must draw the conclusion that cheating is indeed immoral and undesirable.
So basically "do unto others" but phrased needlessly complexly?
Kant's wording scales up to include the emergent properties of a society which operated according to that rule.
The Golden Rule doesn't cover cases like, "Should I throw this trash in a lake." because there's no concrete person being "done unto". Kant's rule does: Would you want to live in a world where everyone threw trash in the lake? Probably not.