It would be pointless to discuss anything with a poster who's only purpose is feign being amenable to evidenced argument so that he can tell you that you failed. As for dictating, yes, he is powerless to do so, but that doesn't mean he isn't trying, and you can be certain how such a discussion will progress. YOU are not allowed to make assumptions, but he puts no such constraint on himself. Why would anyone other than a perennial doormat like Charlie Brown enter into such a discussion?
I have an answer to your last question.
First, there's no doubt that he has no expectation of convincing the likes of you and me that any of his assertions are correct. So why waste his time? I submit that we are not the intended audience. The idea is to chip away at "belief" in science and sway the weak minded to his pov. The motivation? I don't want to speculate, but usually money appears somewhere when you look into such things.
So what is the point in refuting his arguments? Just a waste of time? We'll never convince him of anything? True, but if I can prevent just one undecided person from being convinced, then it is worth it. You are doing a great job with your approach (attacking his "debating" methods rather than the actual substance) btw.
Why I suggested an in depth exploration of just one of his claims was to keep the focus in one place. If we allow him to hop from one subject to another, we will not get to demonstrate the falsity of anything. And if we can clearly show the error of one claim, it may be inferred that the other claims can be refuted as easily. It doesn't matter if he himself is not convinced. He's not the audience.