Should they take "One nation under God" out of the pledge of allegiance

In my opponent's 2-sentence argument, he makes 2 main points, 1) "that is how it was first made" and 2) "This nation was originally Christian." Both of my opponent's arguments are based on the flawed theory that "one nation under God" was always in the Pledge of Allegiance. According to history.vineyard.net, the original Pledge read as follows: 'I pledge allegiance to my Flag and (to*) the Republic for which it stands, one nation, indivisible, with liberty and justice for all.' It was not until 1954 that the words "under God" were added into the pledge. My opponent then goes on to note that "This nation was originally Christian." However, this reasoning is illogical and impractical. While the majority of colonists/ citizens of the young US republic were Christian, that has absolutely no bearing on the decisions we should take today. In addition to being Christian, the majority of early Americans were also slaveholders. From my opponent's logic, we should not have abolished slavery because this nation was originally slave holding; this is simply absurd. In addition, in the Constitution it specifically states that the government has the ability to "make all laws which shall be necessary and proper for carrying into execution the foregoing powers, and all other powers vested by this constitution." This "Elastic Clause" has one very specific purpose: to allow laws to change and improve based on the current times. Ergo, according to the Constitution, we are not bound by any of our previous (non-Constitutional) laws/policies. Now, my opponent twice posed a single question to me: Why should "under God" be removed? The answer is very simple: it violates one of the main principles this nation was founded upon, the separation of Church and State. By combining religion with the government, we are violating the one of the core beliefs of this nation. Pew research refers to the pledge as "an unconstitutional "[slap] in the face" that suggests to those who do not believe in God that their "religious belief system is wrong." The fact of the matter is that these words are a gross violation of the First Amendment, specifically the phrase "Congress shall make no law respecting an establishment of religion." Not only do these words respect the establishment of religion, but they assume that 1. There is a God and 2. There is only one God. These beliefs are not held by many Americans: we are not a Christian nation. According to ffrff.org, in 1797 America made a treaty with Tripoli, declaring that "the government of the United States is not, in any sense, founded on the Christian religion." According to the US Census, over 20% of Americans are not Christian. These words are oppressive to dissenting beliefs. In short, 1) My opponent is ill-informed and provides made-up facts 2) The words "under God" in the Pledge of Allegiance violate the American value of separation of Church and State 3) "Under God" forces all Americans to express beliefs towards the nature of God that a significant amount do not hold Keeping "under God" is an enormous violation of everything America stands for and *can not* be ignored.