At the risk of offending the conventional wisdom here, I do tend to agree with you.
I’m not advocating revenge cheating, but I don’t think it’s automatically wrong or even counterproductive. It really just depends on your objectives.
Once the contract is broken at that level (initial spouses infidelity), there is no more contract, and the BS is no longer beholden to any loyalty/fidelity, unless/until a new contract is agreed-upon.
If the intent is to divorce, then it really doesn’t matter anyway. But if it’s unclear if the path will be D or R, and the betrayed spouse feels the need to sleep with another, I’m not automatically opposed to it.
It may or may not help the BS, and it may or may not end up complicating or tanking the chances of a potential reconciliation.
if the intent is just to inflict pain on the wayward spouse, I think it’s pointless and stupid, because as others have said, the level of pain and trauma inflicted will never be equal. But if that’s what a betrayed spouse needs to try to move forward, then so be it.
I don’t know that I could ever reconcile after a physical affair, but if I were to try, I’m pretty sure I’d need to go down that path to attempt to rebalance the scales to some degree (obviously it will never be fully balanced again).
I think the way to do it though, would be to be upfront and above board about it. “You betrayed me and destroyed me and our marriage, and now you want a chance of reconciliation. I’ll consider it, but in the meantime here’s what I’ll be doing… You can accept that that’s part of my healing process, or you can choose not to. But this is what I’ll be doing and this is what I need to help heal and to bring some amount of balance back to the equation to be able to even try moving forward with you.”