Is it funny to you how cultures disagree about rudeness?

I have had experience with several cultures in both work and friendship. I find it funny that people do things that from my culture is very rude and unaceptable but in theirs it is okay and they say they are so polite in everything. Do you find this funny. Some examples. in Hong Kong everyone knocking into each other when walking. or is that just city folk.Also it is funny that o tourist bumped me in the mtr and said excuse me. NO local would do that. Or the Arabs that it is polite to belch after eating. this is consider rude in the west. Is this funny to YOU?