This question is totally loaded. Whether they like you or you like them (which is what the first half of the description discusses) is irrelevant.
The question could be evaluated more objectively if it were just left to the headline: "Is it rude to leave an interview early if you have already made your decision?". The answer is no, of course not, as long as you're don't do it rudely.
The question could be evaluated more objectively if it were just left to the headline: "Is it rude to leave an interview early if you have already made your decision?". The answer is no, of course not, as long as you're don't do it rudely.