This is very hard for me to admit to, but in addition to being a pagan for over 30 years, I was also very much into the world of fetishes and alternative lifestyles such as BDSM and other disorders. I won’t go into a lot of details, but my understanding and experience has been that a fetish or such an inclination as you find in D/s is not a static thing. Like many drugs and alcohol, the desires gradually but surely escalates and grows in both a need for more intensity and frequency. In many cases it can become the reason for interaction in a relationship more so than love or other healthy causes for being together.
The person in theirself and who they are, is not so much the reason for being with them but the fact that they share the same needs as you have, the love for the fetish etc is far more important then loving your partner. There is a very high rate of going from one partner to another, which is far more the norm then a continuous ongoing commitment. Again, in my experience and research both during and after my own participation in this very different world, if anything the multiple relationships statistics would be much much worse then even the dismal ones of modern marriage.
We all have preferences and things which attract us about others or which we enjoy doing with others more then some things of the same sort. That is just human nature. But a disordered attraction or desire to the point of being considered a fetish and more important to you than the person you are interacting with is a snare of the devil. It would pay to remember that often something seems trivial or not a big deal, but it can grow and overwhelm our fallen natures.
Like many other things, the Church doesn’t always ABC stuff for us, and it can be hard to understand why. However, in the case of something like this, I feel that the guidelines are more in a positive nature rather than a you can’t do that one. If you follow the instruction of the Church concerning relationships, sexuality and matrimony, and apply whether or not something fits into those guidelines, the things which do NOT fit in become strikingly obvious. I would like to say in closing, that, to me, a glaring giveaway is whether something you want to do respects the human dignity of your partner and is a unitive act which glorifies God in His gift of love and human sexuality. Most fetishes and other alternative lifestyle characteristics truly do not if you examine them closely.