"For this you know with certainty, that no immoral or impure person or covetous man, who is an idolater, has an inheritance in the kingdom of Christ and God. Let no one deceive you with empty words, for because of these things the wrath of God comes upon the sons of disobedience" (Ephesians 5:5-6).
It seems that in our wishy-washy world of "don't ever judge anyone for anything," we've lost this sense of certainty that some people are, without question, lost. We've been deceived with empty words, thinking that we can remake God in our own image — a god who is non-judgmental and accepts everyone regardless of how they choose to live.
We are not being judgmental when we simply refer people to what Scripture teaches. God is the Judge; we are not judges. However, we are able to "know with certainty" what Scripture says is the truth about God's judgments: "no immoral person… has an inheritance in the kingdom…"
This modern lack of knowing "with certainty" surely affects our efforts at evangelism, also. If we aren't sure that people are lost, then we cannot present the certainty of the gospel message with clarity. "Repent" is a signal command of the gospel, but it is obscured by our lack of conviction regarding the problem of sin and its consequences. If "I'm okay and you're okay" and "God just accepts us as we are," then the message of repentance becomes repugnant and offensive. Consequently, the gospel itself loses its relevance.
Empty words have indeed deceived. We need to "know for certain" that Jesus is both Lord and Christ (Acts 2:36), and we need to "know with certainty" that people are lost without Him. This is the basis for the fire that ought to be lit under our feet to teach the good news of God's grace.
"For we must all appear before the judgment seat of Christ, that each one may receive the things done in the body, according to what he has done, whether good or bad. Knowing, therefore, the terror of the Lord, we persuade men ..." (II Corinthians 5:10-11).