Joe,
I appreciate your concern regarding divisiveness in the churches, denominationalism, and witch hunts. But on the flip side of this there are the uncompromisable aspects that define who are Christians. Simplified they are below.
 
1. Do they Preach the same Jesus? This goes into the Lordship, and Humanity of Jesus as well as his relationship with The Father and the Holy Spirit. As well as his death and resurrection. This first test is where groups such as the SDA, Jehovah's witnesses and even Mormons fail.....Thus by definition, they are not "Christian".
 
2. Do they preach the same Gospel? Salvation comes via repentance and belief on the part of man, and the grace and Mercy of God, And the blood of Christ to cleanse us from all sin. Repentance is the act of turning away from human striving (fleshly obedience or disobedience) to making Jesus the Lord of your life. Belief is by faith, and involves confessing with your mouth that Jesus is the Lord. None of this is a work on our part, but a change of heart. Many religions fail this, because they add to salvation works of the flesh. In other words, "you are not saved unless you were baptized into the catholic church." Or "You are taking the Mark of the beast if you worship on Sunday". There is nothing we do to merit and or earn salvation. We can, however, have it taken away if we do nothing with the gift given us. and we can lay up treasures in heaven through our obedience to Jesus and his commandments. In other words, we are Judged by the Fruit of the Spirit...Notice they are not even our fruit.
 
3. Do they seek to exalt man above his created purpose? This last one is the one that we see the least in the world, but the one that will play out in these end times. This manifests most commonly in humanistic teachings that are taking hold in the churches, as well as the exaltation of men above other men. To give examples, the Ceasars of Rome were god men, the Pope is considered an intermediary between God and man, Satan's deception in the Garden of Eden, saying you will be like God. In its more moderate forms this is pride of man, and the exaltation of his doctrines to those of God's doctrines, as my last two letters here spoke of.
 
I am in unity with all who believe in the same Jesus, the same Gospel, and the right relationship between man and God. How any of these interpret the rapture, or what day we are to worship, or what food we are to eat etc. are not salvation issues. But if someone believes a different Jesus, then I will call them out for what they are, and that is a None Christian. If I do not do this, they will never come to see the error that they are following. In effect, you are saying that we should call an SDA member Christian, even though they believe in a different Jesus and a different Gospel than the one of the Bible. Their blood will be on your hands if you have the opportunity to confront them and do not.
 
In fact, what some of these "cults" want the most is to be classified as "mainstream Christians". That they are no different than any other denomination out there. Unfortunately, the denominationalism and the elevation of the doctrines of man have led to this denominationalism and Schism, as you so correctly pointed out. How can we say this is what it means to be a Christian, if we cannot with one voice say what is a Christian? That is why, we must look to those who are not in the business of church to unify the True church of Christ followers.
 
This is why I wrote the letters on Social constructs here, that one can see what is, and is not a social construct of man. Is the Calvinist or the Armenian correct? Or are both partial truth and partial error? How about the Baptist vs the Lutheran? Or the Pentecostal vs. the Methodist?
 
My Opinion..... Pride is what keeps us apart. Each holds a partial truth, and when we join in humility, the fullness comes to be known. This is the "promise of unity" that Paul spoke of in Ephesians 4, and why he so adamantly opposed the exaltation of himself, or Appollus any other man, in 1 Corinthians 1-4. Though I do not endorse any TV evangelists, the following video has a strong message on this, and understanding what is the good ground, where a seed will germinate and produce fruit. I will Close with that video.....God Bless, and thank you for calling needless "heracy hunting", but understand that there is also the needed kind.
 
  http://www.theblessedlife.com/series/you-are-here/episodes/lordship