To have a moral social structure.
Ben Shapiro argues this based on the assertion that before morality can be formulated it needs to based on function; and function can't exist without a creator of the functioning object.
Oh, Ben. You're a sharp tack on most issues...but you always succumb to the venal stupidity of the theist when it comes to religion; making the same irrational arguments.
Sigh...You do need a function, but you don't need a creator.
I, am a human; if we follow Aristotelean logic, my humanity is demonstrable because of my function: to survive through reproduction; through the promotion of my species in service to its preservation.
Now, HOW do I guarantee my race's survival? Well, I could advocate for a tournament system of butting heads, but, that's been proven to only produce a few men and women of distinction; the rest relegated to Betas and Cetas or Zetas. Our hominid ancestors did that: until along came some smart ass who realized that, instead of humpin' and dumpin' the females of his species after a battle royale for sexual supremacy, he could garner their sexual approval through monogamous intimacy. The alternative being a society where the alphas simply ignored their progeny, the result being a severely limited capacity for our species evolution. The "survival of the fittest!" is an illiterate summary of Darwin's theory of Evolution. His contention was that their existed a natural hierarchy and that genius would be self-determine. This could be aptly summarized as, the "survival of the most capable". Brute strength and impulsive carnality were not tenable for our species' evolution, so, these patterns of behavior were gradually abandoned. This model of behavior did not allow for a liberal diversity of thought or industry, so, it went the way of the dodo and beta max.
Why did this happen, specifically? Because we realized that our survival had to come from individuals collaborating with one another; and not just to make kids and abandon them to the wild. Now, what best promotes a system of competent collaboration? One in which there are universally observable and thus defensible codes of behavior, a shorthand for societal decorum. This is manifested in a society's values, standards, manners, traditions and sense of human rights. Thusly a new tradition was born, and a society that saw rights as inalienable emerged; enunciating that those rights were not granted by the peoples' appointed governors and government, but were universal and immutable to any citizen with a fully functioning brain. This was in keeping with the law of moral neutrality, aka "the golden rule". Don't do something to someone unless you're prepared to have them respond in kind. Do unto others as you would have done to yourself. Pretty damn simple and airtight logic.
This society motivated individuals, through the enshrining of these universally observable rights, to protect it; and they have continued---despite socialist demagoguery and corportatist conspiracy---to preserve it.
The men who were arguably some of the most informative voices in its construction---Jefferson, Paine, Franklin, etc.---were indifferent if not atheistic in regards to the existence of a Creator. And, even if they weren't, ethics do not begin or end with God. If such were the case, by abrahamic logic, then God wouldn't have killed Christ. Why else would an infallible and omnipotent being sacrifice his own child unless he HAD to, in order to satisfy some cosmic principal or law? Ergo, morality---even by Christian standards---supersedes God. It's based on what's observably functional behavior in the promotion of human life which seeks to preserve itself. The most functional and versatile means being the promotion of free-thinking, liberal and industrious individuals, motivated, therefore, to preserve the human rights of others, and thus their own.
I didn't need a fucking God to reason out what's demonstrably functional, Ben. I did that all just looking at human biology and our most primal instinct: to reproduce. Respecting people's rights---having rights---motivates others to do likewise. The acquisition of virtues enhances my capacity to reason and thus expand my understanding of human rights and human kind in all of its socio-political nuances; as well as address its existential needs. That yearning for context as a day actor on the cosmic stage. No creator was necessary to comprehend and enrich myself through the maintenance of my function. Humans involved to be high-functioning primates because our sentience, as time has long attested, has facilitated our survival.