I did find it interesting that in this day and age an allegedly injured spouse was taking such a retrograde course against an errant mate, especially this allegedly injured spouse, but that's a matter for other boards, not this one.
I don't think we've reached a place where citing adultery in a divorce case is retrograde, and I can't imagine what reason could be more justified and germane. We don't know enough to apportion blame and it isn't our business to do so, but we can still condemn adultery committed behind the spouse's back, not for the sake of condemning the adulterer but of recognizing that failing to uphold a commitment is dishonorable. If you're suggesting that it's ironic that a sex columnist is taking this step, I might agree there given my impression that they're not exactly defenders of traditional thinking on male-female relations, but I don't read her so I don't know.
Anyhow, Jayne makes five great points.