Though that may be true, I don't think that's the reason why, especially when the opposite is more true from my experience. Been all throughout asia for various reasons and everyone hates mainlanders for this very reason you point out. Majority (expats, tourists or whatever) are often rude, disrespectful and look down on non-mainlanders. We have an influx now of chinese nationals in our country and they're literally doing shit like letting their kids shit in our parks (in a VERY upscale area too) or engaging in a lot of very low class behavior or being openly racist.

You can argue who started who, but that's not the reason at the end of the day (on who looks down on the other more). And to be frank, from my experiences with mainlanders I'm more inclined to see it as the opposite, but of course I have my biases