Lyons worked for a company that has an abusive culture. They recently had two top people in management leave because of unethical behaviour - and you observed and promoted aspects of such a culture in your book.
I think that you are getting just criticism, and you are taking it quite badly.
HubSpot fired two senior managers because they tried (foolishly) to use deception to obtain copies of Dan Lyons' book before it came out. You seem to be implying that our book promotes such unethical behavior. Again, I'm unconvinced that describing a program for allowing employees to expense networking lunches constitutes encouraging an abusive culture.
Not even close. Speculation is fine as long as it is labeled as speculation ("I suspect..."). It's nothing like what Lyons did, which is to misleadlingly paraphrase the contents of a book.
> I think that you are getting just criticism, and you are taking it quite badly.
I think his complaint is totally understandable, and I find the personal nature of your criticism bizarre.