I see exactly where your coming from. Who wants to fight for a W who being ran throw by some other guy? And when she does eventually come to her senses. Are you still going to want someone who did all of this? In my sitch my W is an EA for the most part, but it was a PA when it started. If those two were still going at it regularly physically, I would have filed the D papers myself months ago. Right now I'm hanging in there due an EA, which might be just as bad as PA. But I'm hoping that the reality by being in EA from a distance of hundreds of miles will make a difference.
Try to resist punching the guy in the face. But its alright and perfectly normal to feel this way. If your W is truly laid up with this clown on your anniversary, while still married to you. Then maybe you should consider just moving on.