Actually, if anyone stands in breach of contract, it's the student. Dental schools require that their students sign a "professional code of conduct" statement. Everyone at my dental school had to sign one. It's a committment to the idea that healthcare providers and professionals are held to a higher moral and ethical standard than the general public, and an introduction to the idea of a professional community. This kid signed one. Some schools are more "draconian" in their enforcement of these statements, but by and large, they encompass everything from academic dishonesty to professional misconduct. Basically, the school can do whatever they want if this statement is violated, since it is a contract. Imagine if this had been a different situation. The kid publishes comments about another dentist, which his currently unpopular professor probably is. That dentist's patients read them and stop going to him. Defamation of character leads to lost income, lawsuit, kid probably loses, and probably has his license suspended. It has nothing to do with free speech, since nobody stopped the kid from writing his comments. They merely had consequences. Hopefully this kid will learn his lesson before it costs him anything more than a bit of pride.