IF everything you teach is true, but you are simultaneously affirming people who teach things completely contrary to what you're teaching, and in fact are teaching heresy, then you are a partaker of their wicked works. It therefore nullifies and makes your proclamations hollow. It doesn't make them untrue; it makes them hollow. It makes you a hypocrite.
Why is "guilt by association" such a difficult concept for most Christians to deal with? There is a law of "aiding and abetting." You do not need to commit the crime in order to be guilty of it. So if a well-known Christian, who knows better, or ought to know better, is shaking hands with and associating themselves with known false teachers, it speaks volumes against them. They ought to be calling that individual out while face to face.
"If anyone comes to you and does not bring this doctrine, do not receive him into your house, and do not give him a greeting; for the one who gives him a greeting participates in his evil deeds." 2 John 11
"Do not participate in the unfruitful deeds of darkness, but instead even expose them." Eph. 5:11
"Do not be unequally yoked with unbelievers. For what partnership has righteousness with lawlessness? Or what fellowship has light with darkness?" 2 Cor. 6:14
"Can two walk together, except they be agreed?" Amos 3:3
"A little leaven leavens the whole lump." 1 Cor. 5:6
When dealing with truth, if what is said and presented is true, knock it off with accusations of bitterness and having a vendetta! People who do not have biblical or factual objections to what's being said, perhaps you should cease objecting. You might learn something. Otherwise it's nothing more than emotional babble.
"Believers in Christ who remain in such "churches" are dishonouring their Lord. Should they answer, "practically all the churches are the same, and were we to resign, what could we do? We must go somewhere on Sundays." Such language would show they are putting their own interest before the glory of Christ. Better to stay at home and read God's Word than fellowship with that which His Word condemns." A.W. Pink"That argument I have heard hundreds of times when people have been urged to come out of false positions and do the right. But what have you and I to do with maintaining our influence and position at the expense of truth? It is never right to do a little wrong to obtain the greatest possible good . . . Your duty is to do the right; consequences are with God." Charles Spurgeon"Ah, my dear brethren! There are many that are deceived by this method of reasoning. They remain where their conscience tells them they ought not to be, because, they say, they are more useful than they would be if they went 'without the camp.' This is doing evil that good may come, and can never be tolerated by an enlightened conscience. If an act of sin would increase my usefulness tenfold, I have no right to do it; and if an act of righteousness would appear likely to destroy all my apparent usefulness, I am yet to do it. It is yours and mine to do the right thought the heavens fall, and follow the command of Christ whatever the consequence may be. 'That is strong meat,' do you say? Be strong men, then, and feed thereon . . ." Charles Spurgeon"As soon as I saw, or thought I saw, that error had become firmly established, I did not deliberate, but quitted the body at once. Since then my counsel has been 'Come out from among them.' I have felt that no protest could be equal to that of separation." Charles Spurgeon"One thing is clear to us, we cannot be expected to meet in any union which comprehends those whose teachings on fundamental points is exactly the reverse of that which we hold dear. Cost what it may to separate ourselves from those who separate themselves from the truth of God is not alone our liberty but our duty." Charles Spurgeon"Long ago I ceased to count heads. Truth is usually in the minority in this evil world. I have faith in the Lord Jesus for myself, a faith burned into me as with a hot iron. I thank God, what I believe I shall believe, even if I believe it alone." Charles Spurgeon