Agnosticism IS the most dishonest position

[R00tKiT]

Correct, I'm telling you that in a harm based moral system - if an open marriage is not harmful - then it's not wrong.

Okay. And that's a good indication that harm based moral systems don't work.

There may be other morally relevant facts.  Maybe we can take harm away and an open marriage would still be wrong.  It's up to you to suggest what those other relevant facts might be, if you wish to contend....as you do...that infidelity is wrong as a matter of fact.

I already explained why open marriage cannot be right, it betrays commitment. Commitment is by definition not admitting any third party at any stage.

-and yet people in open relationships can be as and even more committed to their spouses than people in a "traditional marriage". 

Aw, that's touching. I don't know if you really think this stuff through. The thing is, a caring husband would prefer commiting to his one and only spouse, rather than pick up these values from a (bitch) third party being around.

Why would I?  On account of the simple fact that those peoples very existence is deleterious to your objections?   Tough luck.  They exist.  See above.

I am aware they exist, pal. The thing is, these people are engaged in an immoral, invalid engagement, no matter how sweet and fantastic their *relationship* is. If you feel like you need to take into account every existing relationship out there you think is too cute to rule out, you might want to consider purchasing a new, more efficient moral system.

Maybe you need to hear the gentle sex's opinion about bringing in third parties to learn commitment.