Not to detract from your point—it is valid—but here in Israel, I constantly hear radio commercials with exaggerated American and Russian accents. It sounds very funny to me, an American, and I'm in no way offended.
By the same token, my wife and I are quite fond of mimicking the way Israelis speak English (and their diction.) Recently heard example, in which a man was speaking about his dog: "I grew him."
But are you willing to do that impression in front of an Israeli? What about adopting a Chinese "Me love you long time" accent in front of a Chinese person? Not to press the point but just because some people are amused by it doesn't mean that it's ok. It was just a really badly done commercial in my opinion because once you dig deeper into it you find that there's no joke here, just people speaking funny.