Preachers ought to preach the word. First I am not smart enough to preach anything else. If I preach on politics a lot of you know more about that than I do. Same with social issues. Secondly, I am smart enough to know that God will richly bless if His word is preached.
Faith comes by hearing.
If we are not preaching God's message we have no business preaching. Jonah's message was not popular but it was the truth, it was from God. Just one minister to 120,000 people. When one minister gets into the righteousness of Jesus Christ and has a personal saving relationship with God, he becomes a mighty instrument and great things come. Jonah was a Born Again Christian.