You may believe that Secular Humanism is something "new under the sun," but it was an idea in the Aegean Sea area of classical Greece. Protagoras said, "Man is the measure of all things" (homo mensura). It goes earlier than that to the plain of Shinar in Gen. 11:4 where men sought to "make a name for themselves.""For though they knew God, they did not glorify Him as God or show gratitude. Instead, their thinking became nonsense, and their senseless minds were darkened claiming to be wise, they became fools..." (Romans 12:221-22, HCSB).
The essence of humanism: glory to man in the highest: the deification or exaltation of man, and dethroning of God. Humanism 101: "Up with man; down with God, because we can do good without Him!" What they mean is to start with man as the measure or standard and judge everything accordingly: Instead of starting the rationale with God--"In the beginning God..," they commence with man and his finite cerebral capacity, whereby God is infinite and the Greeks said that the finite cannot grasp the infinite--how ironic!
"In all his scheming, the wicked arrogantly thinks: 'There is no accountability since God does not exist" (Psalm 10:4, HCSB). "...[All] is thoughts are, 'There is no God'" (Psalm 10:4, ESV). (God is in none of his thoughts!) When you take God out of the reckoning man becomes depraved without limit and God gives them up to go their own way--yes, even man's brain or intellect is depraved and is incapable of spiritual apprehension: "No one understands" (cf. Rom. 3:10f). "...My people do not understand" (Isaiah 1:3, NASB). "...So the people without understanding are ruined" (Hos. 4:14, NASB). "...The whole head is sick, and the whole heart faint" (Isaiah 1:5, ESV).
Secular Humanism is defined as a religion without God in the equation. It is completely incompatible with the Judeo-Christian worldview. Humanists do not believe that there is a supernatural and deny any deity or divinity of any notion in their reckoning. When you take God out of the equation man loses focus and orientation, and has no moral compass to guide him and sees a distorted reality: such as Eastern religion seeing all reality as Maya or an illusion. Humanism is a religion with high priests, meetings, and even has the Humanist Manifesto of doctrines to adhere to. And John Dewey was one of the early proponents who introduced the ideas into our educational system and is the so-called father of American public education. They even have "Secular Humanist of the year" awards! Their chief tenet is that there is no absolute moral code to live by and we are capable of concocting our own morality.
America is entering the New World Order (or era): Trump vows to keep God out of it [politics]. Humanists want a world without God and any religious influence--even banning signage of the Ten Commandments in courtrooms and schools, taking the motto "In God We Trust" off our coins, and "One nation under God" off our pledge of allegiance (they have already banned Bible reading and classroom prayer in public schools in 1963, when infamous atheist Madalyn Murray O'Hair protested and litigated). Will we have a National Day of Prayer and a prayer breakfast at the White House? They are opposed to Christianity because they cannot stomach the fact that some people are "lost" and need salvation, and they believe in their Humanist Manifesto II of 1973: "No deity will save us, we must save ourselves."
Their faith is in science, or should I say "scientism," which is using science for non-scientific purposes such as finding ethical, philosophical, and religious truth (an example is saying that the cosmos is all there is and all there was and all there ever will be--Carl Sagan). They are people of faith too--in the scientific method to solve our problems and lead to all truth. There are not people of faith and people of reason or rationale, because everyone has faith and starts with some presupposition they cannot prove.
The building block of the "religion" is evolution and they regard any encroachment upon this dogma as heretical and intolerable. For example, Carl Sagan said that evolution is a "fact", not a "theory." Note: It's unproven and unprovable since history is nonrepeatable, there are no witnesses, they cannot account for the origin of life nor the arrival of the fittest, and a new species has never been observed to evolve in either the fossil record or in real time.
Humanism is indeed a religion, though they say it is not because they don't believe in "God." But even John Dewey said in A Common Faith that you can be "religious" without having "religion." Atheism has been declared a religion by the Seventh Court of Appeals! Humanism is more than disbelief in God; it's anti-God and, as a worldview, interprets everything without God in the picture, which is contrary to the rise of Western civilization. We might call Secular Humanism a post-theological worldview and they are in the process or rewriting history--a red flag!
A fundamental repercussion of their worldview is that God never intervened in history (Jesus is seen as a legend, myth, lie, etc.), and worse yet, man is not created in the image of God with a soul and spirit, but is a materialistic, naturalistic hodgepodge of atoms colliding with no divine purpose--life has no meaning or purpose (words anathema to them), and, since we are animals in heat avoiding pain and seeking pleasure, we can feel free to live without moral restraint, hell to shun, nor judgment to fear, just like animals and feel no "guilt," which comes only from religion. Note: We are not a freak biological accident or some fluke of nature! In scientific parlance, they are monists, not believers in dualism like Christians, in that they don't believe we have a mind, separate from our brain, but it's only a projection of brain activity and there is no soul or spirit within us.
The whole point of Secular Humanism is to be good without God and to be religious without so-called religion! They deify and exalt man and dethrone and ignore God, making a name for man and blaspheming God's name! Idolatry is not giving God His rightful domain!
So what? Secular Humanists want Christians in their camp, but they must be willing to privatize their faith, not flaunting it or making it public--keep it in church! What we are beholding is the secularization of our society where "man has forgotten God" (Will Durant, humanist historian). The Constitution guarantees the free expression of faith or religion with no State interference or regulation. Playwright George Bernard Shaw said that "no nation has ever survived the loss of its gods." Dostoevsky said that "without God, all things are permissible:"--this is our future? Caveat: Secular Humanists pin the blame for our problem on man's preoccupation with the spiritual element and mostly fault Christianity! Soli Deo Gloria!