How often do you hear "I didn't know that, and it's a good point" in political discussion? When hypothetically, there's no reason you should hear it less frequently than in scientific discussions.
One of the great casualties of modern political debate is that citizens mimic professional politicians, in that the sole mode of discourse is argumentative.
When in reality, if I'm faffing about on HN I would much rather learn something than "win."
It's not like dang steps in at the end of every debate to award the winner a gold trophy.