honestly that's just the way they are. usually if they're born, or at least if their parents are born in say Vietnam or China (or Laos or Cambodia), that's just the way they were raised.
Now, Asians who were born here (2nd gen American) usually have better manners, however Asian's usually grown up and hang out with other Asians so the rudeness just kinda rubs off.
now "white wash" Asians, Asians who grew up around white people are not generally rude.
I know this 1st after being with a viet girl (my ex, and first 2 boys mother) for nearly 10yrs and being around her family probably 60% of the time.
Then, besides her (before her and after her) 80% of my gf's were Asian, so I'm kinda used to it.
I also speak some of the languages, and the languages have different tones that are different from "American English" or "oxford English".... Japanese is the same way, although I've forgotten most my Japanese (but viet and tagalog I can pick up easy.. although tagalog isn't harash at all)
Now, Japanese and Korean are usually super SUPER polite, even though Japanese sounds harsh (my voice is super suited for Japanese cuz my voice is deep and ruff, but Korean sounds like "water flowing over pebbles in a stream".
Hope this helps...
experience in this field Level-10 haha