I think there's a difference between accepting that infidelity happens in a context and blaming the betrayed spouse for it. And there's also a difference between acknowledging that a SSM causes immense suffering for the HD partner and making that free hall pass for infidelity. Just as there's a difference between acknowledging that out of incredible suffering there is a chance for more honesty and closeness, and being glad that the affair happened.
I think we're called to look at our situations with a longer term view, and sticking in victim mode (which I actually don't think, May, you are doing) means holding on to these simplistic views, rather than accepting that it is extremely complex.
I also think that if there ever is a moment where someone looks back on an A and sees it as a catalyst for long term positive change, expressing that thought should be left to the betrayed spouse and not to the unfaithful spouse.
So I can see what you're saying. But I do think that generally infidelity happens when an immature and entitled spouse applies a bad coping mechanism to a broken marriage. And the immaturity and entitled behaviour is entirely the responsibility of the wayward spouse, but the responsibility for the broken marriage needs to be shared. Otherwise the betrayed spouse remains a powerless victim. And we're not powerless or victims unless we choose to be.
