Think about the next company who considers hiring this guy. Perhaps they'll think "hm, what if he doesn't like being with us - will he derail us in public, too? Perhaps we can find a less risky candidate".
Exactly. These things are ugly and this is a cautionary tale for anyone looking to work for a new startup but it's also really important to keep from looking like a bitter employee who will turn on you and make you look evil if things don't work out.