If someone knocks on your door and requests the use of your toilet, you must allow them access

RCW 70.54.050 Exposing contagious disease — Penalty. Every person who shall wilfully expose himself to another, or any animal affected with any contagious or infectious disease, in any public place or thoroughfare, except upon his or its necessary removal in a manner not dangerous to the public health; and every person so affected who shall…