False Teachers Are Evangelists of Their Opinions

False teachers strive more to win over men to their opinions, than to better them in their lives. Matt. 23:15: 'Woe unto you, scribes and Pharisees, hypocrites! for you compass sea and land to make one proselyte, and when he is made, you make him twofold more the child of hell than yourselves!' They busy themselves most about men's heads. Their work is not to better men's hearts, and mend their lives; and in this they are very much like their father the devil, who will spare no pains to gain proselytes.

~Thomas Brooks, Precious Remedies For Satan’s Devices

That is, false teachers are evangelists of their opinions. Their authority is not the truth, the Word of God.