Do atheists even need an objective moral system?

[Ryantology]

So? What if the person values hypocrisy? Or doesn't care?

As diverse as human social constructs can be, persons like this are rarely tolerated in any of them unless they have the power to outright control the construct or the willingness to submit to a system they dislike. It also depends on how objectionable they find the system and their willingness to actively disrupt it.