For context, the argument in dispute again:
1. If God is not real then there are no moral facts.
2. There are moral facts.
3. God is real.
4. Every non-religious worldview is false.
the argument is valid, but premise #1 is wrong.1
there's no good reason prima facie to believe that #1 is true2. moreover, if it's true, then it proves the existence of god, since there are moral facts 3. since god doesn't exist (at least, since there's no independent evidence that she does)4, then the truth of #1 entails a false fact (or a proposition that's not corroborated by any evidence).
you try to lay the burden of proof on those who want to dispute #1. this is unreasonable. a reasonably skeptical person would require the truth of #1 to be established with some affirmative evidence.5
My responses below are written as footnotes to your words above.1
If the first premise is wrong, as you say, then there exists something other than God to ground moral fact. What is this alternate ground?2
As just noted, the first premise invites the question: what other than God would ground moral fact? Since we know of nothing other than God to ground moral fact we are justified in thinking only God grounds moral fact unless and until we have a more likely alternative
. This line of reasoning constitutes a prima facie reason to tentatively accept the first premise as true.3
You are correct here. If there are moral facts, as you say, and if we admit the first premise, as I argue we should until and unless we find a more likely ground of moral fact than God, then it follows necessarily that God exists.4
If the argument is valid, as you admit, then you cannot deny the conclusion, as you do above, unless you deny the premises from which the conclusion "God is real" follows. You do not deny the existence of moral fact so you must provide a better ground of moral fact than God in order to deny the first premise and avoid the conclusion you apparently dread.
I note that you say the first premise is wrong (or false, I take it) and cite as justification your belief that there is no good prima facie reason to accept the first premise. If you know of no good prima facie reason to think the first premise is true then you are justified to suspend belief
with respect to the first premise but you are not justified in thinking it false or wrong. But in view of my argument above, you do now have a good prima facie reason to think the first premise is true. Since you admit the existence of moral fact, you must also admit the existence of God unless you provide a more likely alternative ground to moral fact.