Here is your post that you say is a summary of the message you have been trying convince them of..
Go back and read the context of that proposed line of conversation I posted here before I attempted to open a dialog with S's upon. Which I then dropped.
Those have indeed been my thoughts regarding the frequently recurring mentionings by S8 and S5 about their mother's boyfriend. But I have not directly conveyed any of that to them except to tell S8 over and over and over again that I do not want to discuss those things and to move onto other more pleasant subject matter. I am certain that xW is constantly pushing OM into their faces, injecting him in every conversation and forcing them into contact with him at every opportunity, as there is no other rationale why OM is part of nearly every thought and reflection they make on any subject now. My ex is waging a campaign to ingrain her A partner into every aspect of our children's lives. Don't tell me about parental alienation!
Instead, my actual reaction has been to let my S's finish their sentence and then to try to steer us all to other conversation topics -- the text above that you refer to was a trial balloon to float a possible approach in hopes of curtailing any further such conversations -- as they have become more and more painful to me.
I am doing a very exemplary job, if I don't say so myself, in a difficult situation in keeping a reign on my emotions, as it is, given the continual psychological warfare xW and her mother are waging to sway my S's to their value system -- which includes excluding their father from their lives. Maybe my reactions are not wise at times, as it is often a no-win situation whichever route I take. But for someone to tell me I am guilty of the very thing I have been fighting against is simply offensive to me.
I invite you to go back through my various threads to get an accurate understanding of what I am dealing with here.