@Christine455 If he gave you a nice written review, his line of thought re stars might have been 'I did not stay so can't say it was 5*, nor 4, 3, 2....' - therefore he THOUGHT 1* was the nearest he could get to leaving it blank.....?
It could well be he has no idea how catastrophic it is for hosts to get 1*. He probably did not intend malice...
It is indeed a problem of the system. Time was, when we could leave the stars blank for no showers, & only rate communication. The fact that we now HAVE to arbitrarily click a star to proceed is opening us all up to low ratings from folk who have to invent their own rules to proceed. I've raised this with Airbnb & the operator said it was a real valid point & he'd pass it on.. but no change yet!
You COULD pm your guest & explain... & ask HIM to ask to get the review removed.......