Do you dispute that wrong beliefs about politics have high utility costs

No

or that a discussion on LW would probably bring clarity?

Maybe.

If LW could come up with some way to counter the mind-killing effects of politics, and develop a mechanism for reliably, repeatably holding discussions on politically charged issues without them devolving into irrationality, well then that would be awesome - LW would have done a great service to mankind in developing such a system. I'm just skeptical as to whether that's possible, since it's been tried so many times before, and so far, never succeeded. I'm definitely not saying we should give up - it's certainly a noble goal - I just think we should be very careful about letting a failed experiment in this direction have a corrupting influence on the successful elements that LW has been able to build so far.