Oh, I was just born a submissive heteroflexible masochistic slut with a preference for medium-husky boyish geeks. Like someone rolled a die at birth and picked my identity off a loot table. Maybe it's genetics. Maybe it's "wiring." Maybe it's magic.
And if it wasn't that way, it's a problem. If society, or my childhood, or my past experiences contributed to my preferences, they're no longer valid. The fact that I like to be cut with a knife is totally hot and cool when it's just some random thing--as soon as I reveal that I used to self-cut, it's probably pathological and I need to address my issues and certainly not play that way. The only healthy fetishes are the ones that you're sure came out of fucking nowhere.
Of course that isn't true. My present bears all the marks of my past, and my past wasn't all hugs and bunnies--not that I'm some sob story, no one's past was perfect. I'm a generally happy person right now, I'm pretty comfortable in my skin, but I'm nobody's blank slate. A lot of my sexuality comes from my past, in good, bad, and neutral ways.
And I think that's okay. It makes me happy now, and anyway I can't get rid of it even if I "should." If I'm happy before I get cut up, while I'm getting cut up, and after I get cut up--that's enough. It doesn't have to be "pure."
This is one of those arguments that's probably not true at extremes. If you've been really badly abused and now you seek out really bad abuse, I'm not nearly enough of a licensed kink-friendly therapist to tell you how to deal with that. Although my belief is that "your abuse disqualifies you from all kink, sorry but you have to be vanilla now" might not be the whole answer.
But if your life was a little rough, and now you like your sex a little rough, probably it's not unconnected, and that's okay.