I think you have answered your own question. It would be a hassle to maintain a cache that is going to go missing. It would be difficult for a cacher to locate it without drawing the attention of group you don't like. I think you need to make your statement about PETA in another way, leave geocaching out of it. There are many other views (nice double meaning don't you think?).
Find a place where a cacher would enjoy going, place a cache there. Keep the game simple and politically unfettered.