I wonder too, but think I know the answer. Your faith is contingent on your own discernment and that must be defended more vigorously than the truth. The parable you are now citing does not address Satan casting out demons, it deals with being a complete follower of Jesus and living the Beatitudes, not just snippets of them. It is about obeying all of the law, not just the parts you have determined to be rightly divided. It is about the call to good works. It is about what you have done and failed to do for the least among us.
The entire parable follows because it cannot be repeated often enough to those of you who see works as a dishonest attempt to bribe oneself into heaven.
A Tree and Its Fruit
15 “Beware of the false prophets, who come to you in sheep’s clothing, but inwardly are ravenous wolves. 16 You will know them by their fruits. Grapes are not gathered from thorn bushes nor figs from thistles, are they? 17 So every good tree bears good fruit, but the bad tree bears bad fruit. 18 A good tree cannot produce bad fruit, nor can a bad tree produce good fruit. 19 Every tree that does not bear good fruit is cut down and thrown into the fire. 20 So then, you will know them by their fruits.
21 “Not everyone who says to Me, ‘Lord, Lord,’ will enter the kingdom of heaven, but he who does the will of My Father who is in heaven will enter. 22 Many will say to Me on that day, ‘Lord, Lord, did we not prophesy in Your name, and in Your name cast out demons, and in Your name perform many miracles?’ 23 And then I will declare to them, ‘I never knew you; DEPART FROM ME, YOU WHO PRACTICE LAWLESSNESS.’
Sure...it doesn’t mean what it says. It doesn’t mean that there are “followers” of Christ, thinking they are casting out devils in His name, and He doesn’t know them, They are workers of iniquity. Sure. Your credibility rating with me has just dropped a good 10 points. I’m sure that concerns you not at all, but anyone reading the passage with at least 2 brain cells to shake together, can understand what it CLEARLY STATES. Deny it if it makes you feel better. It won’t be the first time. I’m sure it won’t be the last.