Treating someone as a liar, however tentatively, can also severely damage reputations, livelihoods, and lives. There is not a neutral option here. (Or at least, a neutral balance is very delicate and hard to find, and your approach is emphatically not.)

And I will point out that the course you advocate places those consequences on the party who, if truthful, has already suffered harm. That outcome is certainly not better than people assuming bad things, however tentatively, about the target of a false accusation would be.