I don't think Train is racist (though he might be), I think he's just ignorant. But he needs to drop the whole "I didn't mean that" argument, because I can say anything I want and then drop an "I didn't mean that" to cover my tracks.
I was offended by what he said. Am I oversensitive? Probably. It comes from years and years of pulled-back eyelids and ching-chong jokes and being asked about the cats and dogs I eat for dinner every single time anything happens.
Asian racism is almost always in my experience followed by a "you're reading too far into it," "why are you making a big deal out of nothing," "learn how to take a joke," and I spent years in silence, wanting to be liked (and white) more than I wanted to stand up for myself.
That's why, even though I do genuinely understand where he's coming from (Twitter is a cesspool, I've said this before), his argument is bullshit.