God said of ancient Israel in Psalm 95:10 “They are a people who err in their heart”.
It is one thing to err in your mind. It is quite another to err in your heart.

This reminds us that there are many people who “have it right” in their minds: they have the right doctrines, polity, procedures, etc., but they are not right in their hearts. As God said elsewhere: “Their heart is far from Me”. The discerning among us may sense that in a person. They “seem” right to many; they may be saying and doing all the right things; have the right beliefs, etc. But the discerning knows there is something amiss here. And it is because the person in question is wrong, not necessarily in their action, but in their HEART.
The important application for us, however, is not necessarily that we point this out in others, but that we make sure that WE are not the person who errs in their heart. Let us make sure that WE are not the ones who are “right” intellectually, theologically, socially, etc. – but not right in our hearts. Be on guard against greed (which is idolatry, the New Testament asserts) and pride (which is the same, putting yourself in the place of God) and other motivations which betray an errant heart. For although this person may do a lot of things “right”, God says in :10 that He “loathes” those who err in their heart!