"If there come any unto you, and bring not this doctrine, receive him not into [your] house, neither bid him God speed: For he that biddeth him God speed is partaker of his evil deed" (2 John 1:10-11). So the pastor with the church sign is actually doing the wrong thing. On top of these verses, we have all the examples and verses that greatly discouraged linking up Israel with any nation around them, especially in one of the closest relationships, marriage. That was not just for the days of old. There is a spiritual application. True Christianity is Israel today. All other religions and even those not properly handling the gospel are pagans.