John the Baptizer appeared to make the path to God straight. His primary mission was to baptize men and make the path to Messiah quicker. Jesus' mission was to the sinner, to teach them a better way.
No one fixes a good item, but a broken one. However, the truth is that we are all broken.
We as evil ones, do not cast out Satan. We cast him out in Jesus' name. This is the only way it works.
Paul uses syncretism to convert the men on Mars Hill. We must be careful in using it, but follow that example.
Paul's conversion was the best for God. He used a critic to prove him own point. There was little way that a constant believer would be listened to. Always be on the lookout for the person on the other side to prove your own point.