To bring this back to OP's question--I agree that this realtor is violating their own ethics code. If they are the lead broker already, speak with the local realtor board. If they aren't, go to the head broker. Or whatever they are called in your area. Head brokers do NOT want issues. They want a clean office with lots of sales. We should NEVER have to put up with slander and libelous attacks from anyone, especially those in our own profession.
The problem here is the entire RE agent commission model, which drives almost EVERY one of these types of problems. I don't know that I have a better solution, but it is exactly the same problem mortgage brokers have--no sale, no dinner that night. It's truly a bad setup, BUT, it cries out for someone in the process to be rational and independent, without fear of losing our own dinner from the threats and retaliation from those who may lose theirs... [ends rant]