No foundation, no morals
There is an intrinsic problem with secular humanism, a clever euphemism for materialism and atheism, that submits that there is no transcendent deity responsible for the creation of the universe, humanity, and morality. It is the philosophy that posits that man is the measure of all things and that morality is magically derived from one's self-constructed conscience. But there is a massive gaping hole in this worldview. If man is the measure of all things and therefore each individual's morals are equal to those of each and every other individual, then you have to automatically put an immoral person on the same level as yourself. It is baked right into the premise of the nonbelieving secular humanist.
From Abdu Murray's book (a man who converted from Islam to Christianity), Grand Central Question:
The same problem that confronts secular humanists when it comes to intrinsic value and objective purpose persists in the struggle to ground objective morality without God. Theists have long argued that atheists lack any grounding on which to base the existence of objective moral values and duties. Now theists do not argue that atheists cannot act morally or recognize right and wrong, they only argue that atheists have no rational basis to affirm that right and wrong exist.
If I am the measure of all things, I have no right to claim another as immoral or acting immorally because I have conceded that that person is also the measure of all things and has an equally valid claim as to what is right and wrong. This is essentially the definition of moral relativism, which began with the Reformation that splintered the Christian world; then the Enlightenment that stripped God out of the uniform Christian moral worldview entirely; then the political, social, and cultural progressives of the 20th century, who were the progeny of secular humanist philosophy spawned by the Enlightenment that gave us the fractured and fragmented world we have today.
Another quote from Murray:
What is missing from every one of the secular humanists in their widely published and endorsed documents isn't the affirmation that humanity has objective value and purpose. Rather, it is the affirmation's justification that is lacking. In other words, it is not the what that is missing, it is the why[.] ... Both atheistic secular humanists and Christians can agree that ugly prejudices are wrong and must be stopped because they do violence to human value, dignity and purpose. But we cannot agree about why they are wrong, because we do not agree about the source of human dignity[.]
Although the vast majority of Americans believe in God, religion has been marginalized by the overwhelming hegemony of secular humanism and has become just another lifestyle choice in a smorgasbord of options that society has come to offer. With each option being equally valid, moral relativism has destroyed the possibility of a uniform and transcendent moral order. Instead, each individual has become a god unto himself, and chaos and discord are the only possible outcomes. With millions of equally valid personal agendas competing with each other based on nothing but materialistic hyper-individualism, truth and moral consensus tragically become collateral damage.