I would make the more limited claim that the existence of irreconcilable moral conflicts is evidence for moral anti-realism.
In short, if you have a decision process (aka moral system) that can't resolve a particular problem that is strictly within its scope, you don't really have a moral system.
Which makes figuring out what we mean by moral change / moral progress incredibly difficult.
In short, if you have a decision process (aka moral system) that can't resolve a particular problem that is strictly within its scope, you don't really have a moral system.
This seems to be to be a rephrasing and clarifying of your original claim, which I read as saying something like 'no true moral theory can allow moral conflicts'. But it's not yet an argument for this claim.
Here's the new thread for posting quotes, with the usual rules: