The thing with "tough love" as you put it, is that it gets to the bottom of things fast before investing too much. There is also a difference I the way one is tough. As I said, I wouldn't necessarily approach people the way I said it but I would be sure they know that I mean business.
Personally if I were your partner I would just find it completely unappealing to be with someone who disrespects my partner. I don't care how good the sex is, it would ware thin if there is no communication between them and my other partners. I think it would be a matter of different approaches to poly and that would eventually end it for me.
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