What I don't get is what they hope to achieve? At best, if they were to win, there are two possible outcomes:
1: Let's Encrypt renames itself to something else, and continues issuing certificates.
2: Let's Encrypt folds, and a dozen clones pop up to take its place.
Either way, the simple certificate market still goes to $0.
Whether they win or not, they've managed to piss off the tech community (as in the people that obtain and install SSL certificates). We see this petty and futile move for what it is, and now on top of that, their CEO has shown they are basically at GoDaddy levels of sleazy, and has only reinforced to anyone paying attention to this that they do not want to be doing business with this company.