Tell him what you just told us.
Tell him that you really don't like how he always argues. How he crosses the line and doesn't respect your opinion.
If he's not willing to listen to that, maybe he shouldn't be your friend...
If you really want to 'defeat' him in his own speciality, debating. I can teach you about the tricks he uses. I don't know if you can somehow use that, but maybe you can at least understand how.
I'll just explain how I win every debate I engage in.
1) Only pick debates you can win.
Never debate for something you know is wrong. Only debate for something you know is right.
2) Admit defeat early on so this dispute never even turns into a debate.
If you make a mistake and someone calls you out on it (starts a debate), just admit your mistake. There was no debate. You didn't lose.
3) If you think you're right, never give up. Keep going. Quitters lose. (This is probably really annoying when he does that)
This works best if the debate is vicious or fierce. If it's a polite discussion, it's better to "agree to disagree". Then it's a draw.
Especially 'trolls' (people that just keep debating to be annoying) are easily defeated by just keeping going. I've gamed online quite a few years and many trolls have just bounced off me. They started trolling me, I took them seriously and gave no quarter. Eventually they gave up desillusioned.
4) Change focus of debate to something you're right on.
This is also not right in a nice or polite discussion. Often debates are about definitions of concepts. Defining the concepts in your way, wins you the debate. If you notice that you're losing on one point of the topic just say: "Yes, you're right, but in this case (side topic of larger topic) that's not true." You admitted defeat here, but very subtly. Your opponent is not going to notice that. The debate just shifts to the special case you mentioned. And that's a case you might win.
I don't advise you to try to beat him in a debate. You could if you know how. But he's not going to like it.
It would be better to just be honest with him. T types generally prefer if you're honest.
Just say something like this:
"Hey, I like you a lot and you're a good friend, but I'm bothered by ......"
)