First, let's get our definitions locked down:
Humanism:
1. any system of thought or action in which human interests, values, and dignity predominate.
2. devotion to or study of the Humanities.
3. the studies, principles or culture of the Renaissance Humanists.

Definition1 makes no distinction between humanity and the individual, which leads to contradictions and abuses of power.  For example, overemphasis on individual freedom can lead to Hedonism and a lack of social concern that can harm or destroy a society.  However, the attempt to equalize society, such as Socialism, greatly reduces individual freedom and achievements.

A fifth-century Greek philosopher, Protagoras, said, "Man is the measure of all things."  That philosophy was taken up by renaissance thinkers, gradually leading to an erosion of faith in God and the elevation of humanity as the highest object of devotion.  There is the belief that humans are basically good or can be made to be -- that humans can attain perfection without divine intervention.  Thus all religions are subordinated to the higher good of humanity.

Humanists claim Jesus as a Humanist.  They point to his love and acceptance of everyone.  He taught pleasant and encouraging things.  He protested social injustice before the leaders of the day.  He organized protests and was surprised when they turned against him and killed him.  He was just another Gandhi.

The real Jesus loved people, but he knew the selfishness and evil in these people too well to trust them.  He trusted only God the Father, whom he spoke with daily.  He knew he had come to die for the sins of humanity and provide a way to be righteous before God, who would raise him to life eternal.  All who believe would have their sins forgiven and receive that life eternal as well.

The real Jesus was not involved with the politics of the day.  He paid the taxes without complaint.  He did not offend the Roman establishment.  He respected the Jewish leaders, but he criticized them harshly for badly representing God.  He was busy building a new Kingdom of God among people -- a kingdom that would last for a thousand years on earth and forever in heaven.

The real Jesus performed miracles through the Holy Spirit -- miracles, signs and wonders to attest to his message.  Later, when he was taken up to heaven, his followers were given the same Holy Spirit to attest to their message with signs and wonders.  It still happens here in the 21st century.