You're right that most interpersonal relationships, even (and especially) casual ones, absolutely require deception and silence on certain matters.

But most humans are not rational and don't desire to be rational. That only harms them, but it can't be helped. In such situations, probably the best way to salvage things and limit the total amount of harm is to play along and deceive them.

Would it be even better to refuse to play that game, to insist on interacting only upon a rational basis, or even to refuse interaction with people dedicated to being irrational? I don't know. I can't even guess. Maybe. But the cost would be terrible.