“Numbers of our good brethren remain in fellowship with those who are undermining the Gospel, and they talk of their conduct as if it were a loving course which the Lord will approve in the day of His appearing. We cannot understand them. The bounden duty of a true believer towards men who profess to reject the fundamentals of the Gospel, is to come out from among them. Complicity with error will take from the best of men the power to enter any successful protest against. When will Christians learn that separation from evil is not only our privilege, but our duty?”
Where this quote can be found:
My Word Like Fire has many helpful articles warning about AA.