The sermon is from Acts 11:21-26. It's the story about where the people who are followers of Jesus are first called Christians. But, to make it more meaningful, one should back up and take a short course on what has taken place. This is what Pastor Josh does.
In Chapter 9 of Acts, Saul of Tarsus encounters the Lord. This is the Damascus Road experience. As soon as he's back on his feet he begins preaching Christ. (Acts 9:20) This made the Jews mad in Damascus and they wanted to kill him but he got away and went to Jerusalem. Saul wanted to join the disciples but they were afraid of him. Barnabas defends Saul (Acts 9:27) to the apostles but still there are those who want to slay him. So, they send Saul off to Tarsus.
After this, in Chapter 10, Peter has a vision from God. In the vision God tells Peter three times, "Do not call anything impure that God has made clean." (Acts 10:15) After this, in the same chapter, Peter is told by the Spirit to go to Cornelius the Centurion's house. While speaking to them the Holy Spirit fell on all who heard the word. (verse 44)
In the beginning of Chapter 11, Peter acts as a testimony to the church at Jerusalem of the Gentiles being saved. Even so, when the church at Jerusalem heard that many at Antioch were being saved, they sent Barnabas to see what was going on. Remember Barnabas, the one who stood up for Saul in Chapter 9? He goes to Tarsus and fetches Saul and they both go to Antioch and remain there for a year. This is when the disciples were called Christians. (Acts 11:26)
Barnabas encountered the 'cold-water committee' at Jerusalem when it came to Saul. But it didn't change Barnabas's conviction that Saul had been changed from the inside out by God. Just like Peter, God told him not to call anything impure that He had made clean. Just like the backed-up drain. The snake was threaded through the pipes one more time. And all was flushed out and made clean again.