You simply cannot unwatch something, no matter how hard you try, right? Well, try watching Earthlings (2005) and see how its images haunt your every waking moment. That maybe doesn’t sound like the best invite to a film, but hopefully it will have stirred at least a bit of curiosity in you. Described as “Horror/Documentary” on the Google box thing that appears to the right hand side of all the web listings, that just about sums it up. Narrated by Joaquin Pheonix.
For a gentler, yet no less horrific tale, see Simon Amstell’s Carnage (it’s very good).