I reached a conclusion a long time ago thanks to Barb and her website, but it's just my conclusion and not based on anything scientific. Correct or not, it gave me peace of mind. I don't think that there's such a thing as a catfight gene, although sometimes I have to wonder. I do think that this fetish is deep seeded and has to do with a strong feminine presence in your early life, e.g. a competitive, strong-willed mother or sister, or aunt, or neighbor. In fact most of us experienced an interest in catfighting or women's wrestling prior to puberty, that is. before we even realized that the motive was sexual. I also believe that the kinds of things that you look for in a catfight say a lot about your relationship with that particular person, subconsciously or not.
You mention having the fantasy of watching your wife getting thumped by another women. I have to wonder if deep-down you resent her always getting her way (BTW, that's called "married life") and would like to see her get her come-uppance sometime. You know that you wouldn't / couldn't / shouldn't do so yourself, so put it on another women -- and get turned on at the same time.
Like I said, I have no scientific data to back up my theory, only observations from sites such as this one for 20 years. Just food for thought.