Teller, yes. :-)
I've seen the horse quote all over the place, used by a lot of different people. It's about as meaningful as if it were used thusly: "You mean that new Stephen King book is a folk tale?" "Well, I ain't ever seen a horse write a book!" If a person uses the word 'folk' to denote everything done only by humans, why bother?
Ian A. Anderson may rub a lot of people the wrong way, but he has a point.
The meaning of 'folk' isn't set in stone, but while there are people who want to change it's meaning (only as it pertains to music) there are a number of people who don't want the term to mean any music sung by humans. The word won't mean anything, and people may forget that a folk song was ever anything but one person's musical expression of 'I AM,' but something that belonged to a community.
People all over are tired of hearing the quotation. I'd guess the 'snide comment' was an pre-emptive strike against someone using it. Me, I'm considering mailing the next person who uses it as an autoritative opinion a Pet Shop Boys CD.