Well, there are two factors here. First, is an interest in (or arousal from) female fighting "normal"? There are a lot of users on this site, and I'd hazard a guess that the substantial majority are pretty well-adjusted individuals. This is no more or less unusual than any other 'fetish' that people enjoy, and considerably less extreme than many. While it's virtually impossible to give a hard and fast definition to "normal", I think in the greater scheme of things there's nothing wrong with this fetish.
However, there's another issue brought up in the original note that hasn't really been addressed. Hunter85 states that catfights are "all than turn [him] on" and that "the catfight is the only source of [his] excitement". He goes on to explain that this is causing both sexual and relationship problems with his girlfriend. IMO, that's a classic example of something that's crossed the line from an interest into an obsession, and in the process has become unhealthy. I don't know where online (or IRL, for that matter) to get advice from a professional sexologist, but honestly in this case I'd say it's a good idea.
Put another way, fetishes are fine. Letting them rule you is not.
-JM