The seller cannot withhold property from a "protected class" individual, and the real estate professional must definitely not be involved should this happen. If this does occur:

Both the agent and the seller may find themselves in breach of fair housing laws.

Explanation:

The seven protected classes under fair housing are: disability, national origin, race, sex, religion, colour, familial status. The Fair Housing Act makes bullying people illegal based

on the above 7 classes. This forbids sexual harassment as well among other things.