Full Idea
To say that individuals are free to choose their own values is more naturally interpreted as meaning that they are free to choose between pre-existent values.
Gist of Idea
It is more plausible to say people can choose between values, than that they can create them
Source
Gordon Graham (Eight Theories of Ethics [2004], Ch.5)
Book Reference
Graham,Gordon: 'Eight Theories of Ethics' [Routledge 2004], p.96
A Reaction
Existentialism seems absurdly individualistic in its morality. Nietzsche was the best existentialist, who saw that most people have to be sheep. Strong personalities can promote or demote the old values on the great scale of what is good.