Refute them to their faces, not behind their backs. If a brother is in sin, GO TO HIM. Write a letter, e-mail him, but this continual mean-spirited hatred of the man by other Christians is sickening.
You require more than the New Testament does when it comes to refuting false teachers and false teachings.
Paul and Peter did it publicly.
I understand that you are battle-weary but the enemies attack is relentless...Thus, the fight must press on. We have to stand firm and contend for the faith.