Tweed, what you posted is an argument for increasing protections for farm animals; not for legalizing bestiality.
the point of it is not necessarily to advocate for either position but to destroy the logical ground upon which the bestial-criminalizers stand. besides, it's sort of a throwaway comment, as agribusiness reform is nowhere near the top of priorities for 99% of people who argue in this manner.
I wish they'd just come out and say that dog-fcking is gross and should be illegal because dog-fckers are pervs, which is how they really feel, instead of embarking on some disingenuous animal rights refrain.