Shane Idleman emphasizes the contrast between the wisdom of the world and the foolishness of the cross in his sermon 'Call Me a Fool.' He explains that while believers are called saints, they can still act carnally, and the message of the cross, which is often deemed foolish by the world, is actually the power of God for salvation. Idleman critiques the modern church's tendency to dilute the gospel for popularity, stressing that true preaching must center on the cross and the necessity of repentance. He encourages believers to embrace their weaknesses, as God uses the foolish things of the world to confound the wise, and to share the true gospel without compromise.