I wasn't going to post but this is just so absurd it is hard not to. I will let other people tell you that you have no argument aside from the vague reference to Christianity being against pre-maritail sex, which has inherent tensions with marriage being belonging to the state and thus your moral definition blurs lines that are not supposed to be blurred, ("Render unto Caesar the things which are Caesar's, and unto God the things that are God's" and all that)...but that is for somebody else.
It is much more fun to point out that when you say "NOT most people on the internet by the way -- they are not representative of the population at large" you are implying that you have access to a more representative portion of the population, specifically the majority (50%+1?) of people you know. Now, either you know and have talked about the ethical dimensions of premarital sex or you are replacing the insufficient sample size of the internet with the much, much smaller sample of "people you know." It is also fun because you assume that everybody else on here only deals with people on the internet and not "people they know."
But that is a tangential point really. You are right, there are universal moral norms and regardless of what a certain population at a certain time thinks they are morally wrong. Slavery and genocide come to mind as two examples. But that brings me to your next statement:
"In Liberia, murder and rape are normal too." My first thought when you said this was you have not updated your knowledge of Liberia since Charles Taylor left power (there is also the idea that you just choose an African country because they are all in the "heart of darkness" but I'll give you the benefit of doubt). So good for you, you said that Liberia is so lawless that murder and rape are relatively common. Except, after reading the rest of your posts that does not seem to be what you mean by "normal." As you said later "normal" is a society specific term. So it seems to be your implication that Liberians believe that murder and rape are morally acceptable or accepted? But, you believe that it is still wrong. Now Liberia is a godless place without any sense or morality (which you define as feeling bad later).
I will have to assume that in your sample population, which the internet does not represent, you have a lot of Liberians you have talked to about pre marital sex, rape, and murder. Otherwise, you are just some twit that would rather stereotype an entire country to try and make a bad (in form, the conclusion is irrelevant) argument.