It takes 2 to tango, therefore both have an equal responsibility in the pain they cause.
It's only one person's commitment and only that person has the power to cause any pain by breaking it.
As I said before, fidelity is worthless if the only reason your husband is faithful is because every woman he propositions says no.
I wouldn't sleep with a married man, but I absolutely reject, in every possible way, the idea that I am in any way responsible for some guy's commitment and promises. I actually find it quite offensive as a concept, even though it's not something I've ever done.
This thread and the posts on it, though, are perfect examples of how ingrained sexist attitudes are. I'm quite sure that people really believe they are not being sexist, even when they are. It really doesn't matter that "the women" are the ones on here, you're still directing the moral imperatives and insults of low self respect at them and holding them equally responsible for a man's own sexual incontinence and broken personal commitment. Making it half her fault.
He's the only one who can break his own commitment. She could be anyone.
At any rate, hold the OW to be "in the wrong" if you like, but ultimately if you do decide to try to rebuild your marriage, she won't be part of that process so you're going to have to accept her irrelevance at some point.
Diluting a man's responsibility is a very good way of making it easier and more likely for him to cheat.