I didnt know that too. I dont know how many Asian know the stereotype.
I’ve got a kiwi mate who regularly refers to the Pakistan cricket team as pakis. He was genuinely unaware that this was derogatory (at least it is in the UK). It raises an interesting question - is it offensive if the person doing the offending has no idea at all that they are being offensive?
I’m aware of watermelons having racial undertones, but as a limey I have to admit I don’t really get it. And I wouldn’t be surprised if many of my countrymen are even less aware. Is it a North American faux pas to serve watermelon to a person of color?