It's a problem when Christians think that what if the person rejects the Gospel. Yes, it's a problem that people rejects the Gospel. Even if you're going to preach the full Gospel as nicely as possible there are people who will reject it. Jesus wasn't rude towards the rich young ruler. The problem was with the rich young ruler's pride in himself and his accomplishments. The apostles preached without compromise as nicely as possible but they still encountered rejection from the heathen.
It's a problem when people decide to water down the Gospel and make it look as non-offensive as possible. Such people can say, "Many won't like you because you don't preach as nicely as possible. You are telling them that without Christ, they're going to Hell." While Christians are commanded to be nice to people but they're not commanded to water down the message. They are told to be gentle as doves but to be wise as serpents. They are called to do good works but they are also told to warn people in love. This "niceness" by modern standards unfortunately begs Christianity to water down the message and not just being gentle and nice towards others.
Do you know that the Gospel was meant to offend? Romans 9:33 and 1 Peter 1:8 quote Isaiah 8:14 that says that Jesus is a rock of offence against the world. The truth that man is wicked is offensive to the worldly doctrine of man being basically good. The truth that salvation is by faith in Jesus Christ and nowhere else is offensive to the worldly doctrine that salvation is by works or that you just need to be a good person to get to Heaven. The truth that salvation changes your life and that true salvation results to sanctification is offensive to people who want a license to sin. All these are meant to offend but it will be worth it for the Christian when they see the Lord Jesus Christ face to face.