Technical aspect: If this story is true and the flight could have been conducted in VMC, I think his actions were a bit stupid in that case. No reason to conduct such a fuss or overreact about it (unless it is an ongoing experience with maintenance in general and he did it to prove a point), just make sure it has been properly fixed for the next flight from home base. Conclusion: inappropriate.
Customer aspect: Just leaving the customers standing like that without an alternative plan for them getting to their destination at hand however is highly unprofessional. Conclusion: very inappropriate.