Christians have to hate all that is evil— all of it coming from the world. We cannot accept some evils that “seem” to help us for our benefit and reject the rest. The LORD said to “Hate evil and love good”. Can a Christian support a false teacher even though he teaches some truths? Can a person drink a cup of cold water—having 99.9% fresh water and 0.1% cyanide and live? Absolutely not. The moment you drink it, you will die because the poison has permeated the whole cup of cold water.
It is the same with a false teacher. Even if he does preach some truths which will be mixed with lies, you cannot get saved and it will push a genuine believer away from Christ. If you know a false Christian, your duty as a Christian is to warn those close to you and those whom you come across. As believers, we have to love the truth—loving the truth is seen by exposing the doctrines of demons—pointing people to the real Jesus Christ and away from people who are preaching a false Jesus.
We cannot be spineless or passive, the saints have to be a lover of the truth and being anchored in it so that nothing can move you away from God’s Word.
How can one know what is evil and what is good? By comparing everything with the Scriptures. Take off your bias goggles and put on your ‘Son’glasses. If you don’t, you WILL be deceived. Jesus and His Word comes first. Be a lover of the truth. Be a lover of righteousness. And, be a lover of God’s Word.