This was on Hackaday (I found it via the Puri.sm subreddit) a few months back. It was almost comical that Deere's lawyers used 'our clients might do something illegal with their hacked tractors, like bypass the DRM we implemented to listen to pirated music and we do not want to be held accountable!' as an argument. I do think that a lot of this can be attributed to ignorance rather than malice on Deere's part, though (Hanlon's razor).