Being verbally harassed doesn't leave much for interpretation. Not that that won't happen in Japan. It's a foreign culture to most reading this thread so it's seen more as ignorance/amusing. Like this would never happen elsewhere and so many are too baffled.
Well for starters I'm not talking about verbal harassment, just similar examples of this kind of cultural ignorance like the guys doing blackface on a variety show and the KFC ad where a white guy gives fried chicken to West Indians, both of which caused a big and largely negative reaction here on GAF. Secondly, isolated examples of racial harassment happen in the US as well. Around the same time that the incident I believe you're referencing was being discussed here a whole bunch of white supremacists were arrested for a plot to assassinate the President in 2010.
The thing I find confusing is that, in both this and the Australian incidents, people think that these things are indicative of a culture of ignorance and racism (which is kind of a racist assumption in itself), but in one case the majority of replies are "oh Japan", and the other they're "THAT'S RACIST".