In one sense, cultural relativism is a kind of truce. We all agree not to argue about religion and politics around the dinner table, out of a pragmatic desire to keep our family together and have a pleasant evening.
But I think if you press most people, we do believe that some habits are better than others. Some beliefs, when held by society at large, make people happier or more productive. Some bits of culture are economically more effective than other, at the very least. Science, vaccination, germ theory, etc.. But then again, whether you believe in the flying spaghetti monster or not is unlikely to make much of an economic difference, right?
To each his (or her) own. People are different, and if we accept that some people are sprinters and some are distance runners, some are poets and some are boxers, that's a form of relativism that has real positive social impact: specialization is economically fantastic. So at some point we're willing to grant our neighbors a degree of latitude in their actions and beliefs.
But on the other hand, consider motivation theory -- what motivates people? What would society look like if everyone was aware of how to get the best out of themselves, and out of others? I for one think it would be a better place. Part of the (unspoken) contract of the Enlightenment, of Science, is that as we answer more of these questions, we are driving closer and closer to a true utopia, to the capability to optimize society, to a place where everyone is happy and productive, where both the individual and the society are stable and resilient.
Fundamentalists reject this contract implicitly, and argue that their teachings, not the scientific method, hold the path to the ideal society. The vast majority of religious people aren't true fundamentalists though... the conflict between religion and science is for the most part a construct of the fundamentalists. Many religious scientists are put in a hard spot, because their science demands that they denounce fundamentalism, but their religion may flirt with it or even embrace it wholesale. How can I explain objecting to a specific, inflexible belief, while not objecting to a specific, inflexible faith? Awkward.
This is where most modern people hold up the white flag. We use cultural relativism as a social lubricant, to allow different people to interact without getting all worked up. It's a necessary (by definition) part of a multicultural society.
But I guess I think it's important to keep in the back of your mind the thought that there might be a real, meaningful difference between two beliefs. And that the belief you hold now, might not be the right one.
...relativism: pretty good, in moderation!