You appear to still have different ideas about properly basic beliefs than I do. You indicated agreement with me that, by your reasoning, you cannot assert that the world exists outside of your mind. To me, this means you are claiming you do not know that the world exists outside of your mind.
Whereas I would say I do know that the world exists outside my mind. I know it in a properly basic way, but the fact that I cannot logically demonstrate it to a determined skeptic does not prevent it from being among the most certain propositions of my knowledge.
You are saying something like “it is conceivable that we could be wrong about these things, even though we can’t conceive of what that would be like”. Generically speaking, we can conceive of being wrong. But to conceive of being wrong in those ways specifically would require conceiving what you specifically say is not conceivable.
I don’t think we have any reason to believe that we are wrong in those ways. But even if we did, those reasons would likely be self-undermining - they would imply that we can’t even conceive of what reality is like, and so we wouldn’t actually have any idea if the reasoning we used to get to that point reflected reality after all. But that’s a wide digression.
I’ll grant that it doesn’t follow strictly from the meaning of “necessary being” or “cause of existence of everything outside himself”. But there’s a long tradition of philosophical arguments that moral perfection actually does follow from necessary existence, given other metaphysical premises which are themselves supported by arguments. (See Ed Feser’s book “Five Proofs for the Existence of God”; I could look up the specific chapter if you’re interested.) And there’s other arguments that the idea of an “evil God” (a necessary being but without moral perfection) doesn’t actually make sense, or is an ad-hoc hypothesis compared to the traditional theistic claim. I’m sure you’d find something you could disagree with in those arguments, but they show that the theist isn’t making the connection baselessly.
Even without those arguments, however, I’m not sure this is a problem. It would be a problem if God’s character could be different. I would totally agree with the charge of arbitrariness if that were the case. But it isn’t - God’s character can’t be different than it actually is. So as long as we have some independent reason for thinking that God actually is morally perfect if he exists, then we can infer that necessary existence and moral perfection are necessarily co-instantiated, even if we can’t explain why.
I think we do have such reason - coming from our partial knowledge of moral perfection via our moral intuitions, compared against the way God has revealed himself in the world. And I think there is enough beauty and goodness in creation, and especially in the character of God revealed in Jesus, to make that inference plausible. (Though, of course, the other arguments help.)
(Yes, that does mean that clashes between our moral intuitions and the way God has revealed himself in the world need to be weighed as well. So, I guess such objections are not quite as independent from the Euthyphro dilemma as I was arguing earlier in this thread.)
I don’t think I’ve actually tried to argue this. The argument isn’t hard, though:
Interlocutor 1: “do you think it is possible for (insert moral atrocity here) to be morally permissible?”
Interlocutor 2: “no, I don’t think that is even possible to be permissible.”
Interlocutor 1: “congratulations, you believe that there is a necessary standard for morality.”