I’ve heard this claim before that it is not possible for atheists to have “objective moral beliefs” because many moral claims are based on religious authority, which atheists do not believe in.
Thus atheists are subjectivists when it comes to morality: each atheist may disagree with the other about what is moral. Obviously this opens atheists up to problems of disagreements, with some who might believe very conventionally “immoral” things are acceptable for them.
This is not of course to say that atheists may not choose to live lives that are some what “moral” (moral, as is often defined by religions)
So, what’s the status of the idea of “objective morality” and atheism?
There’s nothing to prevent religious people of doing the same either, even in the same religion you’ll have disagreements on what’s right or wrong.
You’re assuming that every atheist has a different morality but at the same time assume every believer of one religion have the same one.