It only takes one person who goes ballistic over a bad review to cause problems. Imagine if you were one of the hosts of that guy who keeps reposting his diatribe because someone said he had 'odd requests'...I would hate to think what kind of actions/communications he is directing toward that particular host. Guests have and do threaten hosts, make false claims [after the fact and after the reviews], which can cause real issues for a host.
While I never give great/glowing reviews to bad guests, and have never and will never recommend or say I would welcome back a bad guest, we definitely err on the side of neutrality. I also only would review a guest who doesn't give a review if they were really, truly terrible and a menace to the community, otherwise, I leave it alone. The world and the rules have gotten a bit too strange for complete honestly.