Preference does not affect constituionality, but it does so regarding discrimination. Changing or forbidding something because someone believes differently qualifies as -discrimination-, and for that you can look at any number of groups today which have faced it in the past or continue to in the present... gays, lesbians, blacks, etc, etc, etc. Changing it ONLY because of the religious angle WOULD be discriminating against those who do believe, particularly since that ONE line can be omitted by any first-grader onward without difficulty while inserting it cannot be.