Actually, I think you'll find locals make up the larger proportion of cannabis users in this city today, and quite a few locals support legalization--they just aren't open about it. I'm surprised the city doesn't have an organized legalization movement yet and have considered starting one, but I think it would have more weight if run by locals since they'd be able to air their views in Cantonese.
Interestingly enough, many of the conservative locals you speak of have been drinking hemp seed milk for much of their lives...it's quite popular here.