2 Peter 2:1-3(NIV)
2 But there were also false prophets among the people, just as there will be false teachers among you. They will secretly introduce destructive heresies, even denying the sovereign Lord who bought them—bringing swift destruction on themselves. 2 Many will follow their depraved conduct and will bring the way of truth into disrepute. 3 In their greed these teachers will exploit you with fabricated stories. Their condemnation has long been hanging over them, and their destruction has not been sleeping.Some folks or certain Christian groups love to throw around the words "False Prophet". However, someone isn't always a "false prophet or teacher" just because you don't agree with them or they don't agree with everything you believe. While I do believe there is a legitimate concern for false prophets and teachers out there and as Christians we must "guard our hearts" and use discernment and wisdom and know our Bibles, we also must practice some common sense and grace and be careful not to throw around labels or slandering remarks that aren't justified of backed up biblically.
There were false prophets and teachers in the Old Testament and the New Testament and there have been and always will be those around who distort the truth and misuse the truth either for their own selfish motives or because they have been taught in error, or because they sincerely don't study and search the scriptures with an open mind and Holy Spirit leading to learn the truth of God's Word, but I think our role is to know the Truth, constantly study and search scripture, and pray for God to reveal to us His truth.
Unfortunately, many people read the Bible with their minds already made up or preconceived ideas or closed minds, instead of wanting the Bible to speak to them, they instead search the scripture to try and back up what they already believe and they aren't interested in knowing real truth or being taught or learning or being guided by the Spirit and God's Word.
There have a lot of ignorant or misinformed Christians out there who never pick up their bibles and have any regular study time, they don't attend small groups, bible studies, or sunday school classes to maybe have opportunities to learn, but instead they just are led by their own minds, flesh, or the way they were raised, and continue to live out their Christian lives in ignorance, fundamentalism, legalism, and other types of ways that keep them from growing and maturing in wisdom, knowledge, and truth of God's Word.
God's Word is given to us to study and learn. It is a road map, a text book, a guide, a help, and inspired by God to teach us, equip us, help us, enable us, and guide us to His truth and how we should be living, serving, and growing in our relationship with Him. It is also there to help us point out errors, sins, bad habits, and wrong in this world, in ourselves, and in others.
Yes, we should be on the guard for those who preach and teach false doctrine or don't correctly handle God's Word, but we also need to not be so quick to label someone a false teacher or judge someone a false prophet because we may not agree with them. Sometimes we can disagree with others and it's not false teaching it may just be we are wrong, yes, we can be wrong, it may be that we've not grown enough to understand a certain teaching, or it may be a topic or issue that is a preference and not a direct command. It also may not be something pertaining to a salvation issue.
I've seen too many people quick to judge someone a heretic, false teacher, liberal, sodomite, pagan, or some other religious term for a lot of issues that weren't biblical commands, or issues of doctrinal error. They were simply errors of pride, ignorance, or arrogance. I think God deserves better.
I think the key for all of us is to first and foremost make sure when we read and study God's Word we are open to God's leading and not our preconceived notions or ideas, but we are actually open to God's Spirit speaking to us His Truth from His Word. I also think we need to be wise is not fall for everything every preacher or Christian book author says about others. I am always leery of any Christian who is always bashing or criticizing others in order to make themselves look better. If we are speaking and teaching God's Word in truth and love we don't have to belittle, be arrogant, or prideful. Yes, there is such a thing is righteous judgment and there is such a thing as pointing out the errors of others, especially when it has to do with doctrinal or biblical errors, but we also must follow the example and attitude of Jesus Christ in Scripture who seemed He was only Harsh to the arrogant, know it all, prideful, selfish-motived Pharisees and religious leaders. We need to be careful that we aren't being modern day Pharisees and religious leaders of Jesus' day.
If we know the truth, Jesus said it would set us free, but it also I think will help us discern false teaching and false teachers, but don't forget even in pointing out error or things that are false, we still represent Christ, we still need to act in love, humility, and grace.
1 John 3:18 (NIV)
Dear children, let us not love with words or speech but with actions and in truth.