Vlad,
If it's no one then right or wrong are effectively meaningless and you have to explain your behaviour and it's outcomes another way. You have excluded yourself from any further debate and you have no business using these terms.
You have quite the facility for combining the
argumentum ad consequentiam fallacy with flat out wrongness.
First, even
if any of that was true it would tell you nothing whatever about a supposed objective morality.
Second, of course you can talk about right and wrong, just as you can talk about a painting being beautiful or not beautiful, or language correct or not correct. Provided you don’t overreach into the mistake of thinking that there must be absolute standards for these things for them to be "real" that’s fine. Why you would arbitrarily want to carve out one type of judgment (ie, morality) from this principle is a matter for you, but it’s poor thinking.
If nature decides then that is natural law and you can go onto lawgivers etc.
And for those of us working in English?
Explain why absolutism negates meaningful discussion on right and wrong rather than irrealism.
It “negates” it inasmuch as you’d need to demonstrate that it exists at all before you could talk about it. Where is this absolute morality of yours? Is it attached to some physical property in some way, or is it just floating about like phlogiston waiting to be discerned? Who decided on it, and how do you know that? Which set of supposedly absolute rules should one pick, and why? What role is there for interpretation for rules that are absolute? Etc etc
Knock yourself out trying though.