If they feel disturbed, they should be upfront and tell you about it..
I'm sure you'll not feel offended if they come to you in a friendly way, I think it's better rather than just keep quite and suddenly leaving :D
Not sure how China's stance, but since I'm also Asian (not from China tho)...
Well yeah, at least in my country, Indonesia.
I'm an active cannabis smoker since 5 years ago and I have no intention to quit. not in the near future.
I always believe that marijuana / cannabis / weed / ganja / pot whatever you call it, is harmless. It has the lowest addiction rate compare...