The trouble with expecting online readers to recognize tongue-in-cheek postings is that no matter how over the top they are, there's someone, somewhere, who would say the same thing for real.
True, there probably is someone, somewhere who believes all this stuff (hint: it's my MIL and she forwards EVERY SINGLE ONE OF THEM to me). That doesn't mean the rest of the world has to censor their jokes to the lowest common denominator of understanding.
Now, if it was something potentially harmful...like 'Don't bother seeing a doctor for persistent chest pains...just eat onions!' then yes, that wouldn't be good. But silly jokes like vestigial wings on buffalo I think are fine.
Now I have to tell one on myself: years ago, the Energizer battery company ran a series of commercials. Each one started out looking like a regular commercial, although if you paid attention you could see it was a parody. Midway through, the bunny (the Energizer mascot at the time) would come on thumping his drum and the 'real' battery commercial started.
I was completely taken in by a parody commercial for a foreign film called 'Dance With Your Feet', to the point that I mentioned to my husband that I'd have to watch for it in the theater. Then came the bunny...