Well, there was some reasoning, but it was based on the judge somewhat admitting his own ignorance.
Because the police didn't catch up with this man until after he had already reached home, there's no telling if his blood alcohol level was already at 0.1 when he got there, or if he knocked back a few drinks after he got home. The judge was saying (at least this was how I interpreted the story) that because the man in question was of Asian ancestry instead of European, the judge had no way of gauging from his own experience whether it was possible for someone of different ancestry to raise his blood alcohol levels so quickly. Race doesn't really make that big of a difference, but then I said the judge was being ignorant.
The judge came to the surplus conclusion that race might be an additional factor. The judge would've come to the same decision if the man wasn't Asian. Race wasn't the deciding factor here; it was an offhand additional thing the judge said, and that the journalist who wrote this article exaggerated in the headline to get attention.