“You would love him and show him mercy.”
I agree, I just think that providing truth (Scripture) and urging people to repent is loving them and showing them mercy.
I am not denying scripture is important. But what comes first? The only people Jesus directly confronted like you speak were the pharisees. I would guess your brother knows pretty clearly that he is separated from God (if he thought there was one). What he only knows is who God is by those around him that say they follow Him.... just a thought.