Progressive and conservative are two different approaches for policy. If the truth is known then there is no point discussing it. If the truth is unclear or the implications of that truth are unclear, then there needs to be discussion.
Your example about both sidesism, bringing on an anti vaxxer, is either a deliberate straw man or a minor example that isn’t a good representative of the media trying to discuss both sides.
But your last point I agree with completely. Neither progressives nor conservatives have the complete truth.