Providentially, my desire to address the issue of "moral relativity" coincides with the return of the X-Files to the big screen; and their slogan "The Truth is OUT THERE," captures my sentiments perfectly. You see, Truth, Reality, isn't something that we create within ourselves; it exists independently of us. Moral truth, the right or wrong of an action, exists independently of us. Classic example - the Nazi extermination of European Jews was wrong independent of the Nazis' recognition of the fact. No matter how justified a Nazi may have felt in his heart, no matter how much the Nazi party agreed within their own little "cultural niche," what they did was OBJECTIVELY wrong.
Now the Nazis are about the most extreme example I could give, but they establish the truth of what I'm saying beyond a shadow of a doubt: our only two choices are to agree that there is an objective moral order out there that says genocide is wrong, OR we have to say that the Nazis were justified in following their own moral compass and killing six million Jews. There is no third option. We're either human beings, or monsters. We're Mulder, or we're the Cigarette-Smoking-Man. Either Truth is out there, or anything goes.
And this need to choose doesn't hold for just the example of the Nazis; it's universally applicable: pedophelia, abortion, pre-marital sex, same-sex marriage, taking towels from hotel rooms, fudging income tax returns, polygamist compounds, etc., etc. No matter how attractive or convenient a behavior might be, or how strong an impulse we feel interiorly to engage in it, there is a standard outside of us that we are called to adhere to. The Truth is out there, and if we are to maintain our humanity, we have to seek it out and then live by it. And if we don't want to see our own culture further deteriorate, we have to help our loved ones come to this realization as well. "It's not right for me, but it might be for you; who am I to say?" is as great a threat to humanity as the Nazis were. They were an enemy we could galvanize against, but moral relativism slowly rots us from the inside out - and in the name of something as virtuous as tolerance.