What a relativist really believes (or believes he believes) is that 1) there is no such thing as value (as distinct from mere preference) and 2) there is no such thing as truth. The word "absolute" is merely an emollient, a verbal sedative intended to forestall unhappiness. What after all is the difference between saying "There is no such thing as absolute truth" and saying "There is no such thing as truth"? Take your time.
I get what he means and I agree with the gist. But I wouldn't agree with the suggestion that there's no meaningful distinction between relative truth and absolute truth. For instance, I come into the room and say, "It's cold in here." I'm speaking a truth that's relative to me. It's a real truth (if I had denied it, I would have been lying), but it's not absolute. Someone else might walk in and say, with equal veracity, "It's nice and warm in here." If I say my son is tall, I am saying something true, but not absolutely so. He's tall compared to most men. But he's 2 or 3 inches shorter than his brother-in-law. He's much shorter than the Empire State Building. The commandment to fast during Ramadan is binding for Muslims, but not Christians. The truth or falsity of the statement "It's good to take morphine" depends completely on whether we are speaking of a hospice patient or a drug addict. "Elderly persons are revered," is generally true in asia, but not in the U.S. "Sugar is a precious commodity" was much more true during World War II than it is today. And so on, and so forth.
Absolute truths, such as that rape is evil, that responsibility implies freedom, that men and women are different, and that 2 + 2 = 4 are true in themselves. They are true always and everywhere, and for everyone.
Relativists will generally accept that there's such a thing as relative truth. What they deny is absolute truth. Pace Kimball, it's not a meaningless distinction.