I say this by looking at the events in Acts 10, Peter's vision of unclean animals. Racism was keeping the kingdom from moving out into the world, so the Spirit takes decisive action in a Second Pentecost by falling upon the house of Cornelius.
And even that doesn't settle the issue, as the events in Acts 15 show. We don't typically describe the Jew/Gentile tensions in Acts 10 and 15 as racism, but I think you could make a good argument that ethnic prejudice was the heart of the problem.
And once again, this message preaches in the prison. The greatest obstacle the kingdom of God faces inside the prison is racism. Racial solidarity trumps the church inside the prison. I can talk for hours and hours about all sorts of subjects in our Bible study, but whenever I get to racism I meet massive resistance. It's the only topic I've spoken on that has caused inmates to walk out or quit coming to the study.
Racism is the greatest idol, in Acts and in the prison.
