Have I committed an act of disbelief against a shaykh by saying: "Islam is innocent of him and people like him," because he uttered offensive words, and am I sinful, and what should I do to repent?

A Muslim, especially a preacher, should be pure of tongue and refrain from vulgar speech. The phrase "Islam is innocent of him," which you uttered, is a reprehensible statement. It is not permissible to accuse a Muslim with it, even if he errs or commits a sin. If you meant that Islam is innocent of his action, then the phrase is wrong, and repentance and seeking forgiveness are due to the one you have harmed.