This isn't the danger with assuming good faith.
It's the danger with not updating your behavior when the balance of probabilities shows that the individual/group/organization you're dealing with is acting in bad faith.
Our modern era has so many megaphones blaring into the void that it's become significantly more difficult to determine which ones are overtly lying. Accordingly, it's far more difficult to establish a consensus about who's operating in bad faith.
Again, the failure point isn't with the assumption of good faith. It's with not recognizing bad faith when it's made manifest.