That's a naive statement on biblical interpretation. Very generally speaking, there are two views of biblical interpretation regarding the applicability of the Old Testament:
1) The assumption that anything not specifically reiterated in the New Testament is no longer binding, i.e., the Sunday Sabbath, etc. This is generally a Dispensational hermenuetic.
2) the presupposition that certain Old Testament propositions are still in effect unless specifically abrogated in the New Testament, i.e., certain moral laws and civil laws (but not certain ceremonial laws which were specifically abrogated in the New Testament). This is generally a theonomic leaning covenantal hermeneutic.
Although there are varying degrees of both, I would not assume #1 to be necessarily true. Therefore, it is not legitimate to dismiss something by simply because "that's in the Old Testament."
Also, although I do not totally agree with either the dispensationalists or the covenental theonomists, I still recoccomend the following for more info:
I highly recommend that Christians who are interested in the distinctions I just explained and the whole concept of a new Christian Nation should go to a web site called cmfnow.com (or cmfnow.org?) and check out some books and taped lectures by Greg Bahnsen (see his book "Theonomy and it's critics"). There are also debates such as one between dispensationalist Thomas Ice (?I think?) and convenant theologian Kenneth Gentry.
Also, BSunday, regarding your comment that no one is murdering Christians today (in America). This is false. There are literally millions of unborn babies beng murdered today by the will of the despotic, unelected Supreme Court. (Jesus said that we must be like one of these little children).
And, BSunday, you never answered the question as to why the American Revolution was justified anymore than secession would be justified today. It is no answer at all to simply respond by stating, in effect, "Well, that was different". After all, a diffirence that makes absolutely no difference is in fact no difference at all.
1) I meant to type "Saturday Sabbath.
2) the correct spelling of "hermenuetic" is "hermeneutic". (I don't usually make too big a deal about typos since I make quite a few when I type and post fast, but the word "hermeneutic" is an important one).
Excellent post.