I'd honestly never heard the word used as a slur before. Perhaps that's connected to living in the southeast, where we have a lower percentage of Asian-Americans than other area of the country, but still. On the other hand, I've heard the phrase "chink in the armor" (used without any racial intent) hundreds of times at least, probably thousands. Also, I was checking results on google, comparing how common the terms were, and the full phrase seems to be much more common online than the slur, best I can tell. Should it have been used? No. But seriously, the reaction to this has been overblown for what was pretty clearly an honest mistake.