It's hard to know how to comment on this because there's a huge range in what might really be going on. You might be a bozo. He might be a bozo. You both might be bozos. Or maybe you are both pretty good and both just bad communicators.

So without really having any insight about what's up here, I have two pieces of advice.

Ask a lot of questions to understand why he thinks what he thinks. The job is not to explain to him why he's wrong; the job is to ask enough questions that you understand why he's reached some specific conclusion.

And focus on getting things done. Forward progress tends to get everyone aligned and give you something specific to talk about that's productive. If in the "blah blah blah" he's telling you 'this will never work' then you have proof positive that he's wrong. Great. If in the "blah blah blah" he's telling you that your solution is not re-entrant and it's going to crash then you are going to find out he's right.