Just read it. That is a very bad source. It does the same thing you did and just made unverified claims with no actual evidence. It also makes leaps in logic (e.g. "The word was meant to convey, at that time, the inferiority of Asian products to European products. By extension, Asians are also inferior to Europeans.") It makes no mention of "rice boys" and so can't support that claim either. In fact, while I've been doing your due diligence for the last hour, I haven't found an appropriate historical source for any of this. Not on Google Scholar, not on Google proper, nor in my university's library. The closest thing I've found for "rice boy" in particular is the dubious book of definitions that Wikipedia is using as a source for that claim. And the closest thing I'm finding for racist connotations of "rice burner" is from the book Far Eastern Tour which outlines its use in Korea by Canadians in reference to Korean support troops. Of course, the Oxford Dictionary has some information concerning the American etymology, but it is paywalled so I can't access it.

And how dare you accuse me of rewriting history when you won't make the slightest effort to research it yourself. What a shameful display of hypocrisy.