The church must not tolerate false teachers. They teach doctrines that will damn men's souls.
False teachers can disrupt and even destroy the church.
Like yeast in bread dough, error spreads from one person to another. Apostasy is the end result. Allowing one to be a teacher or a leader in the church when he teaches error or is involved in sin is wrong. Tolerating such an individual by remaining silent is to sanction the sin and the error. The false teacher himself is wronged when his error is not refuted.