Atheist or otherwise, the objection to "so help me God" is valid, as is an objection to any deviation from the exact oath of office specified in the U. S. Constitution.

U. S. Constitution

Article. II.

Section. 1.

Clause 8: Before he enter on the Execution of his Office, he shall take the following Oath or Affirmation:--"I do solemnly swear (or affirm) that I will faithfully execute the Office of President of the United States, and will to the best of my Ability, preserve, protect and defend the Constitution of the United States."


Note that a precise, specific, and exact wording is prescribed, and there is no allowance for, no reason for, and no justification for, any deviation from the specified precise set of words there.

John