It is within the right of property owners to refuse to sell or rent to non Jews or anybody else they don't want to deal with. It is also their right to encourage others to do the same, as long as he is not trying to force others not to sell or rent to others but is just encouraging it where is the crime? There are lots of secular property owners who would not sell or rent to orthodox Jews and arabs will go out of their way including using intimidation to stop the rental or sale of arab property to Jews. To be truthful I don't think I would feel comfortable with the idea of renting a property I owned to an arab.
U.S. confirms ISIS computer expert killed in air strike (Reuters)
from the article: Prominent Israeli rabbi faces criminal probe over anti-Arab remarks