I notice SpringheelJack quickly picked up on your comment. And why not? To those who deny the reality of evil, the only sin left is "judgmentalism," isn't it? Sorry, but I disagree with you. What we need is a whole lot MORE social disapproval of behavior that is destroying human lives. The children who are the ultimate victims of casual cohabitation and divorce (and the two go hand-in-hand) are voiceless in the whole matter. But they are made to pay the price for the selfishness of their parents, while the adults who might have been able to curb that selfishness by a sharply directed rebuke or two just sit idly by and "mind their own business". . . or perhaps even rent the shack-up couple their spare room.
So instead a child should grow up in a home where the parents hate each other, don't want to speak to each other, and snipe at each other whenever they can, so that the child grows up thinking this is what a marriage is supposed to be about? Good one.
I believe that can be done without being offensive, rude, or overly judgemental about specific situations. Your comments about the arrangements being wrong are, IMHO, correct...your extension of that into the poster's personal motivations and impact to his children went well beyond that.