The bible speaks about variance in two places.
Jesus defines it in Mt10:35
For I am come to set a man at variance against his father, and the daughter against her mother, and the daughter in law against her mother in law.— KJV, Matthew 10:35
And Paul talks about it in Gal 5:20.
 I would they were even cut off which trouble you.
 For, brethren, ye have been called unto liberty; only use not liberty for an occasion to the flesh, but by love serve one another.
 For all the law is fulfilled in one word, even in this; Thou shalt love thy neighbour as thyself.
 But if ye bite and devour one another, take heed that ye be not consumed one of another.
 This I say then, Walk in the Spirit, and ye shall not fulfil the lust of the flesh.
 For the flesh lusteth against the Spirit, and the Spirit against the flesh: and these are contrary the one to the other: so that ye cannot do the things that ye would.
 But if ye be led of the Spirit, ye are not under the law.
 Now the works of the flesh are manifest, which are these; Adultery, fornication, uncleanness, lasciviousness,
 Idolatry, witchcraft, hatred, variance, emulations, wrath, strife, seditions, heresies,
 Envyings, murders, drunkenness, revellings, and such like: of the which I tell you before, as I have also told you in time past, that they which do such things shall not inherit the kingdom of God.
 But the fruit of the Spirit is love, joy, peace, longsuffering, gentleness, goodness, faith,
 Meekness, temperance: against such there is no law.
 And they that are Christ’s have crucified the flesh with the affections and lusts.
 If we live in the Spirit, let us also walk in the Spirit.
 Let us not be desirous of vain glory, provoking one another, envying one another.— KJV, Galatians 5:12-26
So how to we stop variance. We stop it by having an authority over us, having the same authority over us.
So what is that authority, its the inspired bibles.
People want fellowship with other believers and they want to realize their faith through that fellowship. This is how people go wrong. Because the local church generally has another authority than the inspired bibles.
Notice that it says  that all the law is fullfilled with that you should love your neighbour as yourself. If you go to those churches those people become your neighbour. So you dont fullfill the law.
If you start arguing doctrine with them trying to make them believe the inspired bibles they are probably eventually  going to try to devour you.
Paul wants them that troubles us to be cut off , so dont make them your neighbour by entering their churches.