Sigh, I had posted this to Hubski hoping for a debate a cut above what was going on at Reddit. There is nothing "retarded" about the view that educators should not simply define away the whole question of moral realism versus antirealism. How ethical discourse and debate works is very much a live and open question, just as much as the ethical questions themselves. Whatever our ultimate stance on ethical realism versus antirealism (or all of the more subtle position that this crude dichotomy of options obscures) it is by no means obvious which is right.
It is not dispiriting to see people taking a the view that "there are no moral facts". But it is dispiriting to see people treating this as obvious and anyone who disagrees as "retarded". This has been a live philosophical debate for as long as we have records of such things (excepting those times and places where people were too afraid to speak the questions aloud). I'm not aware of any great recent discovery that suddenly makes the answer obvious beyond debate. And yet quite a few people seem to think moral realism is just obviously wrong. To plenty of intelligent people it's not obvious.
To me that just confirms that something has gone awry in our culture - people are not merely siding with moral antirealism and relativism (which could be fine), but they're not even aware that there's a debate to be had about this and if anyone proposes a debate they get written off as an idiot.
And I don't know what you mean by "Plus those are the actual definitions" of fact and opinion. Whose definitions? Who's the authority on this? Maybe they're accepted definitions in US educational institutions, but the point of the article is to question them.