Titus 3:10 A man that is an heretick after the first and second admonition reject;
2 John 1:10 If there come any unto you, and bring not this doctrine, receive him not into your house, neither bid him God speed:
Romans 16:17 Now I beseech you, brethren, mark them which cause divisions and offences contrary to the doctrine which ye have learned; and avoid them.
Would you witness to an adulterer?