I understand your overall sentiment about someone having the ethical standards to withdraw themselves from writing certain reviews, unfortunately not everyone measures up to those personal standards.

If I KNOW I am unable to write a review - whether it's for personal reasons, or professional conflicts of interest, I usually ask the person who assigned me the review to give it over to someone else. Not all reviewers will do that unfortunately.

If you feel you were given an unjust review, I'd try contacting the site owner and discussing the situtation with them, and possibly offer to pay for a non-involved 3rd party to do a new review for them.

Just my 2cents