It is disheartening for an owner who has only 5 star reviews to receive a lowered review because of an unreasonable guest. Guests can become vindictive in their reviews if a host mentions a problem to them out of concern for their property.
I would like a one time option to throw out a lower than average review. That would make owners feel that their hard work and reputation is less at risk from the whim of an unreasonable guest.