The phrase is a violation of religious freedom
Forcing citizens to proclaim allegiance while citing a God they may or may not believe in is presumptuous regarding religious beliefs.
In the Bill of Rights (adopted in 1791), the First Amendment grants freedom of religion.
While one could argue that removing the phrase "under God" from The Pledge of Allegiance would discriminate against Christians and violate the First Amendment, the real violation was when the phrase was added. Even if the phrase doesn't discriminate against all religions, it discriminates against some. The First Amendment clearly grants freedom of religion; it does not specify only certain religions. Freedom of religion is meant to be freedom of all religions and also the freedom to have no religion. The addition of "under God" plainly discriminates against certain religions and people who choose not to have a religion. In 1940, the Supreme Court case Minersville School District v. Gobitis ruled that Jehovah's Witnesses were not required to say the pledge, as it is a violation of their right to freedom of religion, because Jehovah's Witnesses do not believe in pledging to any symbol or object. This decision was influenced by Jehovah's Witnesses refusal to salute the Nazi Party flag resulted in their being moved to concentration camps. The leader of the American Jehovah Witnesses denounced the pledge in American schools in 1935 called for Jehovah Witnesses refuse to participate in the pledge. Taking out the phrase would not be violating the First Amendment by discriminating against Christians; it would be righting the wrong of adding it to The Pledge of Allegiance in the first place.
Regardless of if the addition of the phrase was violating the First Amendment at the time is irrelevant. What's done is done. Yes, the phrase can be removed, but that would also be a violation of the First Amendment. There isn't a tradeoff when it comes to the law. Just because the government didn't see the addition as a violation of the First Amendment back in 1954 doesn't give the present-day government the right to violate it again by taking out the phrase. In 1943, the decision in Minersville School District v. Gobitis was overturned. In West Virginia State Board of Education v. Barnette, the US Supreme Court ruled that the right to freedom of religion and speech do not apply. Felix Frankfurter wrote that "[t]he mere possession of religious convictions which contradict the relevant concerns of a political society does not relieve the citizen from the discharge of political responsibilities." Meaning that having a cohesive nation is more important than one person's political beliefs.
[P1] The First Amendment grants freedom of religion. [P2] Not all religions recognize a God and not all people choose to practice a religion. [P3] Having the phrase "under God" in The Pledge of Allegiance discriminates against those religions and those people. [P4] The phrase violates the First Amendment and should be removed. [P5] Initially in a Supreme court case in 1940, Minersville School District v. Gobitis, the Supreme court ruled that public schools could not force Jehovah’s Witnesses to salute the flag and say the pledge.
Rejecting the premises