Weird conclusion there at that the end, bit extreme no? No, I wouldn't say our system is illegitimate. Of course it is based on English Common Law, but only insofar as that jives with the Constitution that we wrote. Since the First Amendment was pretty explicitly done to
contrast our view on religion with England's (who of course has their own state religion), I don't think is reasonable to conclude that US common law recognizes Christianity as the basis for our law. Arguing that the culture that wrote those laws was predominately influenced by Christianity isn't something we are in disagreement on either, but to extrapolate that to the point where it would be acceptable for a government to erect a Christian monument to recognize that though? I think that's too far, personally.
1) Citations next time, my man.
Don't plagiarize
(this is a joke, please don't take it seriously)
2) Also note the first citation made in that paper, a case where a man was convicted in England of "blasphemy", something that would (thankfully) NEVER stand in the US system today.
3) Note the English citations made
after the ratification of the US Constitution, which of course hold no common law precedent in the US system.
4) That paper having been written in 1890, lists several court cases that have since been overturned, specifically the aforementioned blasphemy laws that was (rightfully) overturned 60 years after this paper was written as a First Amendment violation. Blue laws that they cite were also clarified as being secular, rather than religious, in nature in the 1960's.