Why do you need evidence to write books about a hypotheses you have? Many people do that. And I think he never claimed to know the truth about it, he was just presenting his ideas of how it could be.
You don't have to agree with it. But the lack of evidence doesn't disprove the hypothesis. Yes it doesn't prove it either.
You can write as many books as you like. But if you spend all your energy trying to convince people of your unproven hypothesis, rather than testing and proving that hypothesis, no one has to take you seriously.