Well, nowadays, it's seen hateful by many to condemn sin in other people ! So most people don't dare to tell the truth about sin, and they fear to condemn sin for fear to be called " hateful " !
It's funny how all ancient prophets were falsely accused of being hateful for condemning sin, and it's still the same thing today, but in a more subtle way.
No one should be condemned for telling the truth about sin, in a world where sin is seen as holiness,
and holiness is seen as sin ! We live in a world where right becomes wrong, and wrong becomes right. We live in a world where saints become criminals, and criminals become saints ! This is true ! Just take a look around and in all human history !
So yes, we should always tell a sinner that they are sinning, but with great diplomacy and understanding of course, just like the way you tell little children when they are doing mistakes ! That's why someone needs a lot of preparation before telling the whole truth about sin to other people ! For instance, the Lord called Moses to be a prophet to Israel after Moses spent 40 years in the desert being a shepherd, a student of the Holy Scriptures, a husband, and father, and a son in law !
Jesus began his Messianic minister after he was baptized when he was 30, and before that, Jesus spent many years being an adoptive son, an adoptive brother, a student of the Holy Scriptures with the pharisees in synagogues, a carpenter, a caring companion of Israelis, Romans, Greeks and all kinds of people from many origins, etc.
Anyway, to tell a sinner they are sinning is a minister, and it needs some preparation, for obviously when someone denounces sin, the father of sin will greatly attack that person in return, and will falsely accuse that person, that's fact.
It's a fierce combat against the evil one, and the Lord is by the side of anyone fighting against sin !