I'm guessing this won't be the most popular comment ever made.....
It was the wish of the founder of SSN, Dr. Amity Buxton, that SSN should provide resources for ALL people who find themselves in a mixed orientation relationship. By definition, this provides a "safe space" for people in this situation to meet, discuss and support each other. If you look at the masthead of this forum you will see there are already restrictions on the topics of this forum, i.e mixed orientation issues only. It is an "Open" forum in that it can be accessed and read by anyone, and anyone can register. If/when trolls infiltrate it is the responsibility of the administrators to recognize and remove them.
There is no right or wrong answer, just your path. Others can offer advice but in the end the individual is responsible for deciding how to move forward. I have been involved with SSN in a support capacity for 15 years. In my experience, people who wish to maintain a MOM are often met with negativity and outright hostility. However in some cases it can work, and those who desire to pursue that path deserve to at least give it a try without being told "it can never work".
To be honest it was my decision, over Phoenix' objection, that the new forum be restricted. Maybe part of that is laziness, as if it was open I suspect there would have to be a lot of administrator intervention. Should you chose to read that forum, you may see people heading for obvious train wrecks, or being doormats. Hate to say, not much you say will prevent that even though it may be obvious to you. Often negative comments will just get their back up and prolong the situation. They will have to figure that out themselves if they are really heading for disaster.
And sometimes, people may have found a way to make it work. Remember "I couldn't do that" does not equal "you shouldn't do that". "How can you do that to yourself" is not helpful.
The only way to prevent posts like that, IMHO is to restrict who can post. Anyone is welcome to comment on posts in that forum in this forum if you must.