Sam, I guess you are not a parent, picture this if you may, someone who was 100% monogamous and expected that of their partner until some time after coming into contact with DW. This person suddenly becomes enlightened after an extensive time in the bossom of a particular DW centre and becomes intimate with a DW teacher, guru, lama, yogi or whatever they label themselves on any given day (who is proud of their closesness to Ole Nydahl). Free love as you would suggest would indicate that any intamacy would be open knowledge to both parties rather than shrouded in lies (the case in mention) that were even passed on to the couples children.
DW may indeed be for some but when it comes between people and affects those not involved in such a manner, then its edicts, influences and morals have to be questioned objectively and instances like this brought into the open.
I have seen what I mention above happen and I would not wish it upon any other families but I have no doubt the troubled lambs of this world will continue to the fold of DW. We can all be intellectually disabled at times of extreme stress, grief or during relationship problems therefore we are all open to abuse and those who see their opportunities to abuse mind, body and spirit for their own gain.
I have two things to say in response to this. First of all, relationships end. Very often, it is because one of the persons involved realizes that the relationship isn't fulfilling their needs. Commonly, they find it isn't fulfilling needs they didn't even realize they had. Sometimes joining a new group can be a catalyst for discovering those unfulfilled needs in yourself.
The story of my parent's divorce: my mother realized she wasn't happy in the marriage. This was after she joined a new group. (Not Diamond Way, or any other spiritual group -- in her case, it was St John Ambulance.) She then began an affair with a man from the group, who is now my stepfather. I suppose, what I am trying to say, is I'm sure joining Diamond Way has been the catalyst for some relationships to end. But really, any group will do for this. And monogamy-vs-non-monogamy isn't the issue here, since groups that share the mainstream cultural approach to that issue can play this catalytic role equally well (e.g. St John). From the point of view of a relationship, its the fact that your partner has left you that hurts; it doesn't matter whether it be for another monogamous relationship, or for a non-monogamous relationship. It hurts that they left you, it doesn't really matter whether they left you for one person or two people or so on.
Now, as to the particular case you describe -- there is a limit to what I can say, since I wasn't there and don't know the situation or the people involved. But, I can make some general comments: When relationships fail, people often behave in a less than laudatory way. I think back to when my parents divorced, and the way they behaved then, and especially the pain involved for my siblings and I. I can look at myself, and see that on several occasions, when past relationships of my own have failed, I behaved in a less than ideal manner. Yet, this isn't the fault of Diamond Way, or St John, or any other group which people might happen to get involved in. It's just human nature. People behave poorly in this sort of situation, including Diamond Way people. Diamond Way is just a group of flawed people, striving for enlightenment (i.e. to be better people), but they haven't got there yet. Lying, deceitfulness, etc., are unenlightened qualities. So Diamond Way doesn't encourage them. But all unenlightened beings express them, including myself and many others in Diamond Way.
Lama Ole says that, in terms of sexual ethics, the Buddha only condemned two things: harming others, and incest. Based on that, if people freely agree to take part in an open relationship, there is nothing in the Buddha's sexual ethics which condemns it. But, when you start deceiving others, lying, etc., in sexual matters, that is against his teachings. And it's inevitable that some Diamond Way members at some point are going to fail to follow the dharma in this area. But we can't blame the teachings or the community as a whole for the fact that some members of the community fail to follow the teachings completely. And I don't think that just applies to Diamond Way -- you could apply it to any group of people.
Thanks for listening