Because, apparently, one must use e-cards every now and again to make a valid point...
Meaning, quite simply, that if you're letting the culture decide what's right and wrong, well, cultures change. More than that, if you think that fallen, sinful humanity is going to come up with an acceptable moral code, you really should dig up a history book.
Moral relativism is a farce, though not often a funny one. Those it makes use of today, it may well turn on tomorrow. The one that makes his or her own morality is also free to change that morality, and who can say they cannot?
Well, someone will. Because the farce behind moral relativism is that people will be allowed to choose their own moral code. They won't. Those who support the voices of opposition when they are at the bottom, will be less welcoming to them when they are in the position of power.
Either man will submit to God, or man will create gods. History shows us how that works out.