Well, I would venture to guess that almost nobody knows this, and as such, being PC just creates another item that people can get their feelings twisted up over. I doubt there are many in today's society that commands the title "Master" as a way to demean others, and since "Master" also has several other origins, it could be one of the others as well. In fact, "Master" was also a title given to young men, and still is in formal situations.
I must admit though, being PC offends me, so my outlook on this may be tainted a bit.