Personally, I think we should differentiate between those who have an exclusive fixation on an object or an isolated part of the body such that it and it alone can bring them arousal and/or orgasm (and frankly, I've never known such a person) and those who are merely enticed and excited by specific things, as one part (if an important part) of their overall arousal pattern.
Also, I think we should differentiate between fetishes that focus on inanimate objects or isolated animate objects (like specific parts of the body), and "fetishes" that can best be described as an unusual focus on a certain type of sexual organism (like, say, members of your own sex) - since, to me, it seems like there would be a significant difference in the mechanics of being attracted to a thing versus being attracted to a [living] being (however unusual or uncommon an attraction to that thing or that being might be).
To go further, I think it would be interesting to isolate the triggers for sexual attraction from those for romantic attraction, and determine to what extent they are related. Specifically, I think it would be fruitful to examine the difference between those who treat their fetish as an object with purely sexual purposes, and those who experience romantic feelings for their object (or being) of attraction. There's so much room for study.
None of this is to say that there is anything wrong, nor that there is nothing wrong, with such peculiarities - frankly, I think we are in no position to make such judgments, since our understanding of human sexuality is poisoned by very counterproductive biases on the nature of sexuality. Even so, it doesn't mean we can't study sexual abnormalities in a nuanced, scientific manner, separate from making value judgments about them.
Above all, I definitely think we should learn to differentiate between matters of sexual taste, and impaired psychological functioning. I know that if someone is turned on by something that grosses you out, the instinct is to say "that's sick, there must be something wrong with you", but we shouldn't mean it literally. It's not true in nonsexual matters (can you imagine "enjoys listening to country music" being a symptom of a psychological disorder?), and I think our belief that it's true in sexual matters is [mis]informed by our biases against sex.
