I see what you mean, but I'm not sure. If I started a thread and it got derailed with humor, I wouldn't think it rude. If it got derailed with people calling me an idiot for starting the thread, then I would.
Anyhoo, wrt the OP, I agree with you that not all Asians look alike, but my opinion is affected by having lived in Asia for two decades. Before that, I wouldn't have been able to distinguish among East Asians. South Asians, yeah.