Jesus said...

"If I had not come and spoken to them, they would have no sin, but now they have no excuse for their sin. He who hates Me hates My Father also. If I had not done among them the works which no one else did, they would have no sin; but now they have seen and also hated both Me and My Father." --- John 15:22-24

Out of context it seems like it would be better to tell nobody that sin exist so that they may remain "innocent", but that is not what Jesus is saying here. If you read the full chapter, you will notice that Jesus is talking about the people that have physically seen and heard Jesus, and here he talks about the judgement that will come upon those who "hate him or his disciples".

Jesus also said:

Unless you repent you will all likewise perish. -- Luke 13:3 (NKJV)

Paul wrote the following comments:

For what can be known about God is plain to them, because God has shown it to them. For his invisible attributes, namely, his eternal power and divine nature, have been clearly perceived, ever since the creation of the world, in the things that have been made. So they are without excuse. -- Romans 1:19-20 (ESV)

For as many as have sinned without law will also perish without law, and as many as have sinned in the law will be judged by the law (for not the hearers of the law are just in the sight of God, but the doers of the law will be justified; for when Gentiles, who do not have the law, by nature do the things in the law, these, although not having the law, are a law to themselves, who show the work of the law written in their hearts, their conscience also bearing witness, and between themselves their thoughts accusing or else excusing them) in the day when God will judge the secrets of men by Jesus Christ, according to my gospel. -- Romans 2:12-16 (NKJV)

Now we know that whatever the law says it speaks to those who are under the law, so that every mouth may be stopped, and the whole world may be held accountable to God. For by works of the law no human being will be justified in his sight, since through the law comes knowledge of sin. -- Romans 3:19-20 (ESV)

The Scripture has confined all under sin. -- Galatians 3:22 (NKJV)

For all have sinned and fall short of the glory of God -- Romans 3:23 (ESV)

Paul preached in Lystra:

“Men, why are you doing these things? We also are men, of like nature with you, and we bring you good news, that you should turn from these vain things to a living God, who made the heaven and the earth and the sea and all that is in them. In past generations he allowed all the nations to walk in their own ways. Yet he did not leave himself without witness, for he did good by giving you rains from heaven and fruitful seasons, satisfying your hearts with food and gladness.” -- Acts 14:15-17 (ESV)

Paul preached in Athens:

“And He has made from one blood every nation of men to dwell on all the face of the earth, and has determined their preappointed times and the boundaries of their dwellings, so that they should seek the Lord, in the hope that they might grope for Him and find Him, though He is not far from each one of us; for in Him we live and move and have our being, as also some of your own poets have said, ‘For we are also His offspring.’ Therefore, since we are the offspring of God, we ought not to think that the Divine Nature is like gold or silver or stone, something shaped by art and man’s devising. Truly, these times of ignorance God overlooked, but now commands all men everywhere to repent, because He has appointed a day on which He will judge the world in righteousness by the Man whom He has ordained. He has given assurance of this to all by raising Him from the dead.” -- Acts 17:26-31 (NKJV)

This is also confirmed in the Old Testament:

Deliver those who are drawn toward death, and hold back those stumbling to the slaughter.

If you say, “Surely we did not know this,”

Does not He who weighs the hearts consider it?
He who keeps your soul, does He not know it?
And will He not render to each man according to his deeds? (Job 34:11; Psalm 62:12; Ezekiel 36:19; Romans 2:6; Revelation 2:23, 22:12)

-- Proverbs 24:11-12 (ESV)