I think a married couple should do what they feel works for them. So if going to swinger parties actually makes their relationship better, then that's no sweat off my back. I haven't gotten married yet because I haven't seen the benefits of voluntary castration and domestication--

--so I'm pretty naive about married life. But I suspect I wouldn't be happy knowing my wife, the woman I would want to spend the rest of life with and raise demonic spawns with, was getting banged by some other guy.
I think that even as I would be doing another girl, I couldn't be able to fully enjoy it and all I could be thinking about would be my dick's happy place being invaded and desecrated by some animalistic douchebag. And I would hope and pray that she felt the same.
The whole situation would make me go, what's wrong with ME?--as self-centered as that is. So yeah it would be a blow to my fwagile male ego, like I wasn't good enough to meet her needs--and then that could lead to me being like, well then she can **** off if I'm not good enough. So in conclusion: no, I don't think I could be in an open marriage.