Why are debates fun with some people but toxic and draining with others?

I've been arguing with a guy who acted SUPER INTERESTED but then would pick fights, cool things off and come back again full throttle. In the end it became difficult to mention pretty much anything bc he was very vindictive and belligerent, which made me react by walking away and going silent. It felt like a continual boxing match, which was draining in the end. Now I just tell him I don't have the bandwidth to argue with him.

But other people I'll "argue" with ALL THE TIME about some philosophical point or some technical "why"/"how" thing that gets resolve OR gets shelved till we can each research or ask other members of our mutual work/scholarly/social group for data and clarification. It's actually FUN to have those debates. It's not something I could do with that one guy, despite the fact that we had both agreed to be "just friends" and nothing physical ever passed between us... I don't know why it's so... nasty and awkward. It's not my usual energy at all. :(

What do you guys think?

Why are debates fun with some people but toxic and draining with others?
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