Forgot to mention it back then, but I recently got reminded about the Euthyphro dilemma and how people use it to argue against Divine Command Theory, and that makes my list of worst arguments. It's not that it isn't worth discussing at all - it's an interesting conversation-starter for a lot of metaethical debates - but treating it as the ultimate gotcha that's supposed to Demolish Christians With Facts and Logic is really dumb. There are valid theological frameworks that embrace either side of the dilemma (though I have to say, people who take the pure "it's moral because God wills it" side creep me the hell out), or, as seems wiser to me, argue that they aren't as mutually exclusive as they look, because this kind of causal logic breaks down when we're talking about the creator of everything. It's possible to poke holes in many of these arguments, but that requires quite a bit more subtlety that going "muh Euthyphro, checkmate theists".
Yeah, I got exposed to Euthryphro as a first-year Philosophy student and it quickly became a pretty weak argument for me. It's not that hard for me to see the validity of the middle ground, positing an omniscient, eternal creator who's kind of "naturally aligned" with and inseparable from the Good; basically God being the Good and Good being God. Of course where I fall off is that actually existing, but it makes enough sense to me in theory.
That only works if (like Plato) one believes in the independent existence of universal properties like "Good." If like most people you don't think goodness or redness or chairness are natural properties in themselves but only properties we ascribe to individuals by convention, then "God is the Good by nature" is a meaningless statement. This is why the ur-nominalist Ockham held strongly to divine command theory: he claimed that even if God commanded us to hate Him it would be good to do so.
I think the Euthyphro dilemma is quite powerful and puts the theist in an uncomfortable position - a lot of the intellectual crisis of the early modern period was in trying to make sense of the alien God that a divine command theoretic position produced. And at any rate it complicates the common theist charge that atheism is incompatible with morality.
If we accept that goodness is not a natural property and only a property we ascribe by convention (which, yeah, is basically what I think) then the whole Euthyphro thing becomes irrelevant anyway, surely? Things can't be described as "Good" full stop, regardless of how God figures into it.
Perhaps Euthyphro kind of crystallizes the theist position as inherently Platonic - i.e. believing in independent existence of "Good" like you said - but I don't think many theists would necessarily shy away from that position.
