I had a feeling you'd bring up moral realism, and you're somewhat correct; it's not a necessary feature of moral realism, however, and most philosophers arguing for moral realism have stronger arguments than "that's just the way it is", which usually appeal to our intuitions about other non-moral facts, such as "this chair exists" or "I have two hands". It's up to you whether those arguments are successful, but it doesn't do anyone favours to dismiss them out of hand as you are doing. If they were so patently ridiculous, I doubt many philosophers would believe them. If they make sense by relying on our intuitions about other facts of the universe, I can see why many philosophers believe them.

If you have a solid argument aganist moral realism, I'd like to hear it, even though I'm familiar with most of the arguments for moral anti-realism, and I generally sit on the anti-realist side of the fence these days. But it does yourself a disservice to say that all such arguments are circular and logically invalid. I quite like this argument from the Stanford Encyclopedia of Philosophy entry on moral realism:

"In light of this concern, it is worth noting that the challenge posed here for our moral claims actually plagues a huge range of other claims we take ourselves to be justified in making. For instance, just as no collection of nonmoral premises will alone entail a moral conclusion, no collection of nonpsychological premises will alone entail a psychological conclusion, and no collection of nonbiological premises will alone entail a biological conclusion. In each case the premises will entail the conclusions only if, at least surreptitiously, psychological or biological premises, respectively, are introduced. Yet no one supposes that this means we can never justify claims concerning psychology or biology. That there are these analogues of course does not establish that we are, in fact, justified in making the moral claims we do. But they do show that granting the inferential gap between nonmoral claims and moral claims does not establish that we can have no evidence for the moral claims."