It is written in scripture that we are to expose false teachers and their false doctrines as long as we know for a surety they are false.
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. 18 For they that are such serve not our Lord Jesus Christ, but their own belly; and by good words and fair speeches deceive the hearts of the simple.
Ephesians 5:11 And have no fellowship with the unfruitful works of darkness, but rather reprove them.
1 Timothy 5:20 Them that sin rebuke before all, that others also may fear.
Titus 1: 10 For there are many unruly and vain talkers and deceivers, specially they of the circumcision: 11 Whose mouths must be stopped, who subvert whole houses, teaching things which they ought not, for filthy lucre's sake. 12 One of themselves, even a prophet of their own, said, The Cretians are alway liars, evil beasts, slow bellies. 13 This witness is true. Wherefore rebuke them sharply, that they may be sound in the faith; 14 Not giving heed to Jewish fables, and commandments of men, that turn from the truth. 15 Unto the pure all things are pure: but unto them that are defiled and unbelieving is nothing pure; but even their mind and conscience is defiled. 16 They profess that they know God; but in works they deny him, being abominable, and disobedient, and unto every good work reprobate.