Doctrinal evil is worse than moral evil.
First, let me define the expressions. By “moral evil” we understand all the corruption of sin, like hatred, immorality, impurity, sensuality, idolatry, sorcery, enmities, strife, jealousy, outbursts of anger, disputes, dissensions, factions, envying, drunkenness, carousing, and things like these. The Word of God calls the moral evil “deeds of the flesh” (cf. Galatians 5:19-21). This is the “leaven” in the moral sense (cf. 1 Corinthians 5:6). Of course, this moral “leaven” is a part of the one and inseparable “leaven” of all what is opposed to pure doctrine, because the Christian doctrine is inseparably one, including pure teaching and pure life. As for the doctrinal evil, it is the false teaching, which is once again described by Paul by the term “leaven” in Galatians 5:9. In the context of Galatians 5:9, you see that the topic is the false teaching by which some Galatians were persuaded and deceived, and that resulted in moral evil. In the same way, the Lord Jesus described false teaching (or doctrinal evil) by the expression “leaven of the Pharisees” (cf. Luke 12:1). So doctrinal evil is any false teaching which will naturally lead to moral evil. Actually, in the Bible there is no separation between doctrinal evil and moral evil, because the Christian doctrine itself is both the true words and the right living, and one cannot separate them from each other. Thus in Titus 2 the Apostle Paul explains the “sound doctrine” by talking both about moral virtues and soundness in Faith and in words of doctrine. In our Faith, sound doctrine directly means sound living. You can’t separate the life from the doctrine. But there is a huge error today: people think that if they have some good morals, i.e. some beautiful virtues like love and tolerance and patience, etc. (I mean, virtues according to the world’s standards), then it is not of importance if they don’t have a sound doctrine. This corrupted opinion practically denies the very important biblical doctrine of righteousness by faith alone, as it dismisses the Person of Christ who is the Truth, and claims to be able to be good before God by the works of self-righteousness without the need to obey the Truth. So I will now put a distinction between doctrinal evil and moral evil, because I want to show the difference between Christian morality which is based on sound doctrine and the worldly morality which is based on false doctrine.
Indeed, if you see a person doing good and having a good character (I mean as you see it outwardly), then does this necessarily mean that this person is a child of God, saved from sin to be a child of obedience? Of course not, because God says in His Word that Salvation is not by good works or personal merits, but by faith in Christ. Again, if you see a true child of God doing something wrong, then does this mean that he is lost and that he is not saved by the blood of Jesus Christ? Of course not, because the Bible does not teach that those who are saved become perfect in themselves and do not ever fall in errors, but on the contrary the Bible teaches us that if we sin we have an Advocate, Jesus Christ (cf. 1 John 2:1), and that every true child of God needs to get more mature by growing in Grace day after day (cf. passages like 2 Peter 3:18 and Philippians 1:9). So having a moral evil doesn’t automatically mean that we are lost. A true Christian may have some moral errors that the Lord will correct by His Grace. But if you have a doctrinal evil, i.e. you believe wrong things about Christ and things that are inconsistent with the teaching of His Word, then that’s fatal. The Lord Jesus said: “I said therefore to you, that ye shall die in your sins; for unless ye shall believe that I am [he], ye shall die in your sins.” (John 8:24) So if you don’t really believe in Christ for who He really is, then you are lost. And all what is written in the Bible is about Christ, for the prophets of the Old Testament talked about Him (cf. John 5:39), and the men of God who wrote the New Testament wrote it by being moved by the Holy Spirit who took from Christ and disclosed it to them (cf. John 16:14 and 2 Peter 1:21). Sound doctrine is all what is written in the Bible, and all what is written in the Bible is about the Person of Jesus Christ. If you have a wrong doctrine, then you believe wrong things about who Christ is. So sound doctrine is very important, and doctrinal evil kills you. Imagine that someone believes that moral evil is not bad and will not surely lead you to Hell (cf. Galatians 5:21 and 1 Corinthians 6:9-10); so this person has a wrong doctrine about morality, because he has a wrong doctrine about who Jesus Christ is and about His sanctifying power; so how can you make this person have a good morality?…
Thus doctrinal evil is worse than moral evil. Of course, for God both doctrinal evil and moral evil are bad, that’s why Christian doctrine does not separate true morality from sound doctrine. However God makes it clear in His Word that all sins can be forgiven except the sin against the Holy Spirit. I will not go here into the details about the sin against the Holy Spirit, but let it be sufficient to say that one of its implications is that if you refuse the truth about the Person of Christ then you will not find forgiveness and you will die in your sins, as the Lord said. So although both doctrinal and moral evils are evil for God, yet doctrinal evil has more catastrophic consequences than moral evil. If you believe what is wrong, you will surely practice what is wrong. But if you believe what is right, then even if you do something wrong, you will surely repent of it by the Lord’s Grace, as you have the sound faith. So if someone teaches you wrong doctrine, he will be hurting you much more than if he does some moral evil.
Grace be with you!
Disciple of Jesus Christ
Short explanation adapted from The submission of the wise woman to her ungodly husband.