I've known many highly intelligent people over the years as I'm sure you all have. I find that many if not most of them have a cynical and sarcastic sense of humor. In my opinion, the response from Bob Jones is very in line with someone of his intelligence, who knows this so called competition is very amateur in comparison to the Sanswire airships.
Is it unprofessional? Somewhat, but since it was a reply to a stockholder's email, I don't think it is required to be totally professional. It's more important, in my opinion, to answer the question in a way that will connect to the stockholder so the true meaning of his words are understood, while at the same time, not saying something that will get himself or his company in trouble.