Yes and no. Truth if it remains unknown to man is up to opinion, like god. Some believe in god so much they go to insane lengths to worship god. To them god is truth, and luck is gods will. To others god can not be proven and thus is not real. Acts of god are called luck in this case.
In any event it is hard to play devils advocate when you don't believe in what you talk about. Maybe if I sound more like glenn beck and iggnore the other sides talking points people will believe me? ( sorry but I don't like the guy lol )
The line of thinking I am trying to debate here I have only heard about so I am sorry if I don't debate it well.
If truth is a man made thing like right and wrong then like right and wrong it is up to the person to decide. This only works if both sides of the debate can agree on if truth is a man made thing or not. Because truth is "what is" then that means you can make the debate that truth is around before people just never expressed. Also right and wrong can have something very much the same said about it though that would be more along the lines of "man created right and wrong or god did atleast"
Anyways I don't think I can play devils advocate well this time I am sorry.
Also if you watch anime at all watch Tngn toppa gurren lagann and you will know why I laughed when you said this. "reality is created by opinion? Ie if we all were of the opinion that we could fly then gravity would not affect us?"
Also flying dose not iggnore gravity. ( sorry a little nitpick )
The phrase "X is true to me" has (IMO) two valid meanings
1) I personally believe X to be true.
2) I personally believe X to be true and that belief causes X to be true.
Meaning 1 is not relevant to discussions about what is true.
Meaning 2 has the implication that reality is a social construct that only exists as it does because it is not believed to be otherwise. If (and while for it can cancel itself) meaning 2 is true then the nature of reality is fluid. This is a non-self-contradictory belief.
You did a fine job of presenting the devil's advocate position.
@QuantumT
I see a few more possibilities
Moral Nature of morality
1) Absolute (Morality exists and is not shaped by opinion)
2) Relative (Morality exists as more than an opinion but shaped by opinion)
3) Amoral (Morality is just a man made opinion)
Epistemological Nature of morality
A) Knowable (The Moral Nature and its details, if any, are knowable)
B) Unknowable (The Moral Nature and its details, if any, are unknowable)
1A Knowable does not necessitate provable. In this case we would have a duty to pursue moral action.
1B Unknowable does not necessitate giving up. You can do something without knowing you are. Again in this case we would have a duty to purse moral action. (However this case requires higher levels of humble doubt)
2A [I do not sufficiently understand this view as I defined it]
2B [I do not sufficiently understand this view as I defined it] (However this case requires higher levels of humble doubt)
3A Knowable does not necessitate provable. In this case we would need to replace the fiction of morality with something else.
3B In this case we would need to replace the fiction of morality with something else. (However this case requires higher levels of humble doubt)