The problem with deeming people heretics just because you disagree with them is that you put into question someone elses relationship with the Lord. Say, for example, the Lord told a person to read Joseph Prince's book on unmerited favor, and now you're calling Joseph Prince a heretic. VVhat does that say about that persons relationship with God? Is it real? Does God have two mouths?
VVhen people pull out the heretic card what exactly are they trying to accomplish, beyond defamation? They want people to stop listening to that person because in their own opinion the individual is in error. Yet, what decision must be made for a person God told to learn from said preacher and you're condemning said preacher? Are you bold enough to stand before God and say, "VVhy are you telling this person to learn from so and so? He is a heretic!" Or would you rather question that person's relationship with God? Did they truly hear the Lord?
You see, people need to be careful tossing around such a term. People use it too loosely and no longer is a true heretic able to be spotted because everyone is a heretic. Heresy at its root denies Christ. Jesus is our foundation. Heresy that is damnable ought to be addressed, and yes other doctrines not central to one's salvation should also be addressed but not with such tenacity that it completely obliterates a man's credentials as a spawn of satan.
Some people might find it illuminating to see themselves as the apostle Paul (at the time known as Saul) on the road to Damascus and Jesus appearing before them. Do you remember what Jesus said? The same could be said to the many people defaming God's children, accusing them of heresy and trying to ruin their image. You might glean something from the apostle Paul. Is Christ being preached? Good!
Some of you are doing more harm than good fighting so called heresy. Their position may be opposed to yours, but you've gone from correction to defamation. No longer are you leading into the truth, but lacking gentleness. You don't see the damage you could cause to those witnessing your accusations. VVho will stand to hear the Gospel from a man that they just overheard is a fraud? A liar? A heretic? You're closing ears off to the Gospel in your pride to be right. You aren't defending the truth, you're burying it by poor judgement.