Jesus made it clear that getting rid of an unclean spirit is only a part of deliverance. You must also fill the place that was previously occupied by the demonic spirit with the presence and power of God as protection. If a person is cleansed from an evil spirit but left "empty," the spirit will return with even more spirits and the individual will be much worse off. Simply being empty of the devil, but not full of God, is a very dangerous and short-lived condition. True deliverance is not only getting freed, but also staying free.

Jesus rebuked the scribes and Pharisees and His statement about the men of Nineveh and the queen of the south condemning them at the judgment. One of the laws of God concerning accountability is being dealt with in Luke 12:48, "...For unto whomsoever much is given, of him shall be much required..." The people of Jesus' day who rejected His message will be held more accountable at the judgment than the men of Nineveh or the Queen of Sheba, because Jesus' witness and person was so much greater than either Jonah or Solomon. 

Just as a man who receives miraculous deliverance from an evil spirit becomes more accountable and will end up in even worse condition if he doesn't walk in that accountability, so the people of Jesus' generation were accountable for more than any other generation had ever been. A person would be better off to keep just one evil spirit than to be set free, not fill himself with God, and wind up with eight demonic spirits, seven of which were more wicked than the first. The scribes and Pharisees would have been better off to have never had Jesus bring the kingdom of God unto them than to reject such an offer. He has given us much, what will we do with it?