Peter and John got in trouble because they were teaching the people. They took the message that God had given them and took it directly to the people. Typically teachers would just teach in the temple to the other religious leaders. But Peter and John went straight to the people.
The thing is we've gone back to how the pharisees wanted it. We don't take the message straight to the people anymore. We hide our message up in our own little Christian circles. We shy away from any kind of spiritual conversation outside the walls of the church. Church is where we talk about God, but we don't bring it home, or to our neighbor's house. JM