That reduces it to the statement "our common sense tells us so, you can't prove us wrong, we don't have to prove ourselves right".
This is ultimately the case for all statements.
I fail to see the relevance. Humans convince each other of many things all the time. If we couldn't, we wouldn't be here on this site! There are minds "out there" in mind-space whom we couldn't convince, but that doesn't mean there are such human minds, because humans are quite similar to one another.
Are you seriously suggesting humanity is divided into moral realists and anti-realists, and no realist can possibly explain to me or convince me of their position and even talking about it is pointless?
Here's the new thread for posting quotes, with the usual rules: