>>hn_thr+(OP)
I think what you’re looking for is a high quality conversation: where both parties invest effort in maintaining good faith and are self-aware enough to recognize what assumptions and biases they bring into the debate; where there is a mutual goal of learning, rather than winning; and where the participants are self-secure and mature enough not to need their tribal identity validating.
This is all much more likely to happen outside of the public gaze.
And so I think you are looking not for a website but for a person, or perhaps a website that helps gather such people - and somehow keeps out those who claim to be all of the above but are fooling themselves or the rest of us.
Where do you find good people? There’s probably a market for an “intellectual dating site”.