> If you have a solid argument aganist moral realism
The key counter argument here, as to why the philosophy domain is so messed up, is because of motivated reasoning.
If you could get a PhD in the topic of "does God exist?" I can bet that most of the people with a "does God exist" PhD would say "yes" and they would come up with increasingly complicated and obfuscatory reasons for why that is the case.
Because why else would you go and get that degree in the first place? What, you would spend 4 years of your life, just to get to the answer of "no"?
And then they would say that they are the experts in the topic of God existing, therefore they are right.
A similar thing applies to philosophy. It's mostly motivated reasoning. People twist themselves into convoluted pretzels, all because they really want to believe that the universe proves their morals correct.
That's a much more tempting conclusion, than the boring one of "well, I guess everyone just has axioms, and that's that. We can't re-concile them. Oh well!".
So of course they get to the conclusion that morals exist. Because that conclusion means something. It means that you are right on the most tempting conclusion of truth and aught statements, and math/the universe makes it so!
You can wield that conclusion as a weapon. Of course people want that.
And even better, it can't be tested, in the real world, by definition! How convenient.
And then they say they are correct, because they are the self proclaimed experts on the topic, and if you cannot parse their ever more complicated, or ever more obfuscated arguments, well I guess you are a science denier like everyone else who disagrees with the "experts".
As in, it is literally almost the most perfect example of motivated reasoning. Untestable. Convoluted. Powerful. And by definition the basis for what people should do.
And philosophers just happened to come to the "convenient" conclusion.
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."