If a realtor wants return clients and good will, it behooves them to act in the best interests of purchasers. They also have ethical duties set out by their professional organization, and are subject to discipline. There are plenty of properties to show clients.
Code of Ethics:
http://www.areahub.ca/Members/media/...or_code-1-.pdf
A REALTOR ® shall protect and promote the interests of his or her Client. This primary obligation does not relieve the REALTOR® of the responsibility of dealing fairly with all parties to the transaction.