But when divers were hardened, and believed not, but spake evil of that way before the multitude, he departed from them, and separated the disciples, disputing daily in the school of one Tyrannus.
Note 3 at Ac 19:9: As mentioned in note 2 at Ac 13:14, it was Paul's usual manner to enter the Jewish synagogues to share the Gospel. The synagogues were different from our churches today in that they didn't have a paid minister who conducted the services, and anyone, especially visitors of repute, were allowed to share with those in attendance. Paul took full advantage of this platform.
It was not Paul's desire to start a new religion. Jesus was the Savior of all, but He was specifically the Messiah of the Jews. Therefore, Paul sought to turn the Jews to their Messiah. However, when these Jews rejected the Gospel and began to speak evil of it, so as to turn others from faith in Jesus, Paul separated the disciples of Jesus from the synagogue and continued his teaching.
This set a precedent for us to follow. We should seek to work with all who claim to worship the same Lord. If given the opportunity to minister, we can associate with anyone. However, when people are not receiving and instead begin to speak evil of the truths of the Gospel, it is to our advantage to separate ourselves from that situation.
Failure to follow this example has left many Christians in dead religious churches. They desire to minister to the people there but are given no opportunity to do so. Instead, they are being slowly killed themselves by the unbelief that is preached from the pulpit. This is not the way Paul conducted himself (2Ti 3:5).