"wouldn't it make much more sense to study economics and complex systems to get an idea of what the outcomes of any particular choice of social structure are?"

Ok, well, this is a fine idea in theory, but there are tons of problems:

1.) Actual social structures are way more complex than anything we could ever hope to model - ever. We can't make predictions about them - period.

2.) Even if we could, there is no means, and has never been a means, for manipulating social structures directly. The dynamics of social change are even more complex and less well understood than the structures themselves. At the very least we can classify the structures - the dynamics are a whole other world of complexity. It's not as if we, the intellectuals, are sitting on high and that everyone else listens to us and changes their behaviors accordingly.

3.) Your ideas about economics and complex systems require semantic mapping - they require that we can take a real-life situation, map it into the model, manipulate the symbols, and output a result. Unfortunately, this mapping falls OUTSIDE of the domain of the fields themselves. This is my whole point: one role of Philosophy is the creation of the mapping.

I think you are confusing my -descriptive- claims with -prescriptive- ones. I'm not telling you that ethics is -good-, I'm saying that it is the principal means by which society discusses difficult problems. Ethics, morality, religion, are all ways that society has a discussion with itself, if you want to think about it that way.

Can you give me a good, concrete, example of how you can use math to prove anything about society, without relying on assumptions about what is "good" or "right?"

A large part of what modern philosophy (post-modernism, post-structuralism) (which I am now assuming you are wholly ignorant of) talks about is the boundaries of what we can coherently talk about. A lot of it is hyper-skeptical and actually probably asserts things that you'd agree with (like that we can't claim moral absolutes, they are culturally dependent, etc.). Philosophy now serves as the kind of watchdog of language - it says what we can say and what we can't.

(For instance, the statement "God Exists" is not wrong, it's incoherent. Have you ever thought about it that way? What's god? What does it mean for an undefined entity to "exist?" Does dflskajfk exist? More precisely, it's incoherent in the context of assertions of objective truth. It's NOT incoherent in the context of religious discourse, in which it's taken to be a transcendental truth (axiom). Only by engaging our structural ideas about society can we think about why people "believe in god" and realize that "believing in god" is not a metaphysical but rather a cultural condition)

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"Economics can tell us what are the outcomes of Democracy or Communism or whatever"

No it cannot. This statement is absurd unless you make tons of assumptions.

"like in Democracy, I guess some people will be exploited, but the average is happier, or whatever"

Lots of "whatever"'s here. You really aren't making a good case for "economics." Do you even know economics? Have you taken any graduate courses in it?

"Once we know the likely outcomes, we can apply our values to them and decide which system to use."

Which values do we use?

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""They can't prove their ideas all the way down to ZFC"

I don't think that is true in general."

Do you actually know?

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Look, I don't mean to be mean, but it really doesn't seem like you're interested in Truth per se. You're interested in truth in terms of how you see the world. I guess that's fine (and necessary). I understand what you're saying. I guess problems start to arise when you try to understand what I'm saying (and fail). If you don't want to understand what I'm saying, that's OK too.

You have to understand that from my perspective, your belief in "math" and "economics" and your constant appeals to them as "things" and "bringers of truth and wisdom" seems borderline religious. You might be able to say the same thing about me re: philosophy, but I keep claiming that "Philosophy is not a thing" (and neither is Math or Economics, incidentally), so that wouldn't make sense.

Consider for a moment what it would be like to believe in god. I'm sure you've had arguments about god with Christians/believers. I'm sure they've been frustrating. There's always a sense that you "just can't get through." Consider that perhaps I feel the same way with respect to you. Consider the possibility that you are stuck in the same sort of mind-dungeon that religious people are stuck in. The only tools you have to interpret your world are the tools are you arguing for. You interpret other tool sets in terms of your set of tools. It's like trying to convert someone who uses C++ to use Lisp (have you ever tried?). They say "why should I use that? It's the same! They're both Turing Complete!"

I do not believe that any argument can be non-ad-hominem. We are both people, arguing.

The truth is complex and neither you nor I understand it. The deepest claim I'm trying to make is that I think we should be humble and err on the side of assuming that we don't understand things (until we are absolutely certain that we do). This is what I originally took offense to in your original post - your claim that your "prejudice had been validated." It hadn't been. I don't understand why you are more comfortable saying Philosophy (which you don't understand) is useless and meaningless instead of just saying "I don't understand Philosophy." It's OK to not understand things. (again, I'm not even saying that I "understand" any of these things, but then again I still haven't claimed to)