That was an authority that had to confirm it. Theres a lot of morality that atheists and agnostics take for granted and will try to proclaim are self evident.
But the truth is many of these ideas historically (like sexual consent) are likely relatively new concepts in comparison to how long homosapiens have been around
I agree that atheists and agnostics adhere largely to Christian morals and standards all the while incredulous and sometimes blasphemous in what they say towards the very God that established right and wrong to begin with.
I do however strongly believe in the argument of "malum in se" versus "malum prohibitum" and that both are real and self evident among the sane anyway. When a sane man beats, rapes, or kills a woman for example, I believe that is "malum in se" and that a man inherently knows that what he is doing is deeply wrong or "evil" if you will. Where I differ from a nonbeliever is that I believe that the very reason a man committing those heinous acts, or even a man or woman witnessing those acts; inherently knows them to be wrong is because when God gives people souls at conception that our souls themselves are each imprinted with a conscience that inherently knows right from wrong when it comes to certain acts.
I also believe that because of mankinds fallen and worldly nature, we are predisposed to commit relatively minor sins from very early in life. You never have to teach a small child to lie, to steal, to get angry when they do not get their way. They do this automatically. All of them. Every child. Babies and small children are naturally the most selfish creatures on Earth. They want everything and they want it NOW, and if they do not get it they will cry or act out...until they are trained how to properly act. Its human nature. Conversely the vast majority of children AND adults cannot look a person in the eyes and tell a bold faced lie...at least not without certain "tells" such as staring at the floor, fidgeting, blushing or blinking excessively. Absent mental illness, it takes a lot of practice to become an effective liar. Most people, like both of my kids and myself, are terrible liars and should never even try...because whomever we lie to is 100% going to know we are not being honest with them. This is also because of the conscience of our soul, disagreeing with our brains decision to try and deceive others. We are internally conflicted when doing this, which is why there are outward signs. A sociopath, psychopath etc does not have that internal strife, because part of their brain is malformed or malfunctioning. IMO it doesnt mean that person lacks a normal soul, they just have a damaged brain that short circuits their conscience. This is of course just my opinion, i am certainly not an expert in any field related to these conclusions. Just my 2cents.