"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)
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 17:30-31 (NKJV)
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)