"John said to him: "Teacher, we saw a certain man expeling demons by the use of your name and we tried to prevent him, because he was not accompanying us. But Jesus said: "Do not try to prevent him, for there is no one that will do a powerful work on the basis of my name that will quickly be able to revile me, for he that is not against us is for us."
The above emphasis in the scripture is wrongly placed. The words: "for there is no one that will do a powerful work on the basis of my name" is the crux of that scripture.
The point being that only by God's spirit can such a powerful work be accomplished on the basis of Jesus' name therefore since God's spirit is at work that individual cannot be against Jesus but for him.
There is no contradiction in the scripture..
Sabrina