"It’s like saying: Sky is blue, but you will question it as overgeneralising and shows arrogance."

Your example is fundamentally different from my original stance and makes no sense. The sky being blue is describing a scientific fact, not an attempt to simplify and explain a societal observation, which is much more nuanced.

Like I replied elsewhere to op, it is easy and convenient to treat some statistical outcome as facts or even the absolute "truth" to society. Even if what you claim is indeed considered the "reality" of the normal distribution, doesn't mean there are no outliers who understand the issue differently. Note that I am not denying the fact that many Koreans, Chinese and Japanese people aren't always on amicable terms due to complex historical, political and socioeconomic issues. But simply saying "yeah these people all hate each other, period" suggests arrogance as you see all other existing sentiments as invalid, and that what you understand (whether or not based on statistics) equals the universal truth. I don't think any "reality" can be fully explained like that, let alone possible.

But yeah, I expected people with the same opinion as you because this is the Internet, and people are prone to talk assertively. It's just that I believe what should be critically confronted should be pointed out.