For sure, consenting adults can get really fucking freaky! I'm pretty kinky myself, though I've got a lot of hard lines, too. I went to Torture Garden last year for Halloween and dripped candle wax over a couple of consenting sex workers who actively told me to do it them. I'm not sure I'm going back this year because the party didn't really live up to the name tbh.
The problem with extreme kink and porn is the profit motive. The more extreme the kink, the smaller the pool of performers/workers you have. With that smaller pool comes a greater asking price for the workers. Furthermore, the more extreme the kink, the smaller the pool of consumers become. Now add in the vice tax, by which I mean the social stigma that porn has, and the scuzzier and less ethical the pool of producers becomes. How do scumbags maximize profits within capitalism? They certainly don't invest in their people and they certainly don't invest in their capital. And in pornography, those are one and the same. Porn producers will take advantage of naive young women (and men!) with all sorts of heinous contracts. Add in some human trafficking, runaways, etc., etc..
That is an extreme illustration, for sure, but it applies to both kink and non-fetish porn. And anyway, the exploitation doesn't even have to be that bad. Just think about how much the average job fucks over the worker in today's economy. That is compounded in industries where there are a lot of grey areas and where much of the industry is hidden away from the public at-large.
For the record, I'm generally pro-pornography. Like many things in this country, our reluctance to admit that almost everyone partakes in this "vice" keeps us from being able to make it a safer and more egalitarian aspect of society and the economy. That's why ethical and non-exploitative porn is important. It's not always easy to find, and it's next to impossible to fully vet, and I'm sure there are probably scumbags who claim to be one of the ~good pornographers~; but while there is no ethical consumption under capitalism, we should always try to mitigate the harm we inflict because we are part of a society that has made certain choices.