Your points have what seem to me like pretty obvious responses. If this is actually new to you, then I'm very happy to have this discussion.

But I suspect that you have some broader point. Perhaps you think my overall point is misguided or something. If that's the case, then I think you should come out and say it rather than what you're doing. I'm totally interested in thinking about and responding to actual points you have, but I'm only interested in having arguments that might actually change my mind or yours.

But again, if this is actually new, I'm very interested.

On your actual points:

Not being as sensible as me on these topics isn't the same thing as not being as sensible as me in general.

Sure, but they are also very closely related, and knowing about one will help you make inferences about the other.

without (in effect) first concluding that he's wrong on the topic

There are plenty of excellent ways to make educated guesses about how sensible someone is being in a given area.

For example, you might look at closely or not so closely related topics and see if they are sensible there. Or you might look at a few of their detailed arguments and see if they ask the questions you would ask (or similarly good ones). You can see if they respond to counterarguments in advance. You can see if they seem like they change their mind substantially based on evidence. etc. etc. etc.

But as I said, If this is actually new to you, I'm actually super excited to describe further.