Example: Lying.
Lying can get millions of people killed, displaced, maimed or otherwise ruined for life (e.g. when lies start a war).
Now, of course, some investigation needs to be done to determine whether lies are being told, but that should be doable since the whole notion of lying is that someone is making a demonstrably false claim.
However...first we have to decide if it's okay to lie and start wars or cheat in elections or send innocent people to jail, etc, etc, etc.
To say "they have their view and I have mine; both might be valid" you either have to believe that lying -- in ways that do real harm -- is acceptable, or else you have to believe they're telling the truth.
If it's the former -- if you're saying that their view is that lying is okay and that's just as valid as the opposite view -- then why even discuss? It's all just a horse race; there's no right and wrong.
If, on the other hand, we're really just discussing whether the other side is lying, then at least we might agree that they shouldn't.
But to the extent that THEY think they should, there's a difference that is not susceptible to polling. A difference that should be carved in stone. A basis for declaring unequivocally that those guys are in the wrong, period.