Christ came to Earth to give us the light. He wants us to know and believe the truth and to practice all holiness. This is the heart of evangelism: to bring people to know what is right and help them submit to it. Thus, evangelism means truth. If we promote an error (any error) then we are not evangelizing, but corrupting.
A grave error crept into the minds of many in the Church over the last 50 years that says that we can convert people if our evangelism follows the spirit of the age and compromises the faith with the modernist way of thinking. They actually believe that we should "soften" the truth, or re-work it so that it can be more pleasant to those who hate God. Evangelism is not compromise with the world; regardless of who tries to tell you it is.
The only way that true evangelism happens is if we tell the truth. The truth says that unrepentant sinners do not enter the Kingdom of Heaven, they are given eternal Hell because that is what they chose over God. The fact is that some people reject the truth, and no amount of "niceness" can convert them. If they do not want the One, True, God, then we cannot change morality or doctrine to sneak them in the back door.
We are not supposed to speak the truth with hate, but with love and compassion. Yet, we are still supposed to speak the truth and let those who are headed to Hell know that they do not have to choose that path. This is the message of Christmas; God took on human flesh so that we could take on godliness. Tell them this; do not compromise it. You save no one with compromise, and could very well condemn yourself.