"I would like to ask you this question: Why do Chinese tourists act so loud and uncouth when in Asia, or Europe? Can this sort of behavior be considered civilized?"
I feel "hear" that everything is loudly in China, there are many people and being quiet seems to show that you are not strong enough.
Also a "good" restaurant has many people in it and is loudly here in China,
in other countries its different:
many people in it but quiet is a "good" restaurant.
Your are right everyone have different customs but you still can try to look if it is proper for your surroundings or not