Ah, so it's okay as long as other 'faiths' are presented. I understand there is a statue of the Greek goddess of justice in the very same building that "Moore's" 10 commandment monument stood. Seems to me that criteria has been met.
"They are placed there as art, and are anyway nearly universally considered as myths."
Nevertheless, it is promotion of a religion, which you say is wrong. They must be removed.
There has to be some consideration of intent.
Are there any Supreme Court justices or employees who worship such Greek / Roman "gods" and put the statue there as a religious statement?
Is someone claiming their judicial powers derive from such Greek / Roman "god"?
Is anyone claiming Greek / Roman gods gave us laws that are the "highest law of the land"?
I think not.