Asians are known to have very little people skills. I'm an asian myself, and every time I go to a chinese restaurant, I get the "what you want?" (when taking my order), or "Hah?!" when they didn't hear me.
One time, my husband (he's white) used his Visa Gift Card for payment (he doesn't know the remaining balance on the card), and the owner marched up to our table, handed the card to my husband in a rude manner and said there isn't enough balance in the card. So my husband gave him another CC and apologized. He marched back to the counter where his wife was waiting, and they both mumbled on how annoying people can be, and why even bother to dine out when they have no money (in mandarin). I gave them serious stare, and they instantly knew that I understood what they said.
We walked out the restaurant, and they too pretended that we weren't there. No thank you's, no Pls come again whatsoever. If the asian restaurants that you went to belongs to those from China or Korea, they are usually very rude. But if they're from Thailand, Taiwan or Japan, they are usually more courteous. When I have one single bad experience in a restaurant, I usually never go there again. I don't care for excuses (it was a bad day, not doing good etc), when you're in this business, you're suppose to maintain a good image, and if you can't do that, close your business.
So don't take it personally, it has nothing to do with blacks. They just have bad people/ social skills.