Paul taught that we should exercise church discipline (1 Cor. 5:1,2) and trust God to be the final Judge (1 Cor. 4: 3-5) and Jesus said to expose false teachers (Matt. 7:15-23). To pronounce another religious group to be false can seem a pompous undertaking, especially in a culture that preaches tolerance for everything from homosexuality to a mother's "right" to kill her unborn child. Tolerance is the banner that unites much of our culture and anyone who points a judging finger at someone or something is often ridiculed.
But Christians are told in the Bible to separate themselves from the sinful practices of man and to expose error. "Examine all things and to hold fast to that which is true" says God's word (1 Thess. 5:21). So we do. What does it mean to examine if we do not judge what is right and wrong? Jesus judged the Pharisees as hypocrites. Peter judged Ananias and Saphira as liars (Acts 5:3-4). Paul judged the Galatians as fools (Gal. 3:1). The reason something can be said to be right or wrong is because the Bible has laid out before us a moral and doctrinal standard that is clear. It is wrong to lie. So, we are able to say to someone who lies, "What you are doing is wrong." That is making a judgment.
Likewise, with the cults, as Christians we are commanded to be able to give answers to everyone (1 Pet. 3:15) and to contend for the faith that was delivered by the apostles (Jude 4). If we do not fight for the faith, the faith will be lost. If we do not expose the errors of the cults then the cults will move unchecked in the world and lead even more into eternal destruction.
To make a judgment means that we must recognize that there are absolutes. In a world that worships relativism, absolutes are not welcome and the cults that espouse their demonic doctrines beg tolerance.
Father God, it is my prayer that I show wisdom and love if I ever need to correct or criticise another believer regarding the truth of Your Word. Lord give me the courage and wisdom to stand strong to fight against false teachers and cults that twist and manipulate the Truth of Your Word to justify their perverted and misguided lifestyles and religious doctrines. I pray this all in Jesus' name. Amen.
References: NKJV Holy Bible, Life Application Bible (NIV), the Nelson Study Bible and CARM.