John, one of Jesus’ twelve disciples, once informed him that they had seen an exorcist casting out demons in him name. They had tried to stop him, because he was not following them. But Jesus said, “Do not stop him; for whoever is not against you is for you.” (Mark 9:38-41, Luke 9:49-50)
But at another time, Jesus said, “Whoever is not with me is against me, and whoever does not gather with me scatters.” (Matthew 12:30, Luke 11:23)
These two statements of Jesus were made in two different contexts. In the first one, Jesus speaks to his disciples about how they should deal with people around them. Here Jesus is liberal. If anyone is not following Jesus in a strict sense but is using his name for doing good, Jesus does not disapprove of it. Jesus shows a soft attitude towards people on the periphery of faith. Maybe they are not fully convinced, not completely prepared, but they have an inclination, and they may eventually make up their mind. Jesus wants to keep the door open for them.
But in the other context, Jesus is talking about himself in relation to his adversaries, Satan in particular. Here, Jesus makes a clear distinction. He has come to earth with a mission and he would not negotiate a compromise. One who does not share the objectives of his mission, one who is unwilling to give him wholehearted support, one who is not able to leave everything for his sake, is nothing less than his adversary. Jesus is drawing the battle lines for here and for the future world. As the Bible says, a time will come when all his adversaries will be defeated and the world will acknowledge that Jesus Christ is Lord. (Phil 2:10-11)