To add to that - the underlying problem is the whole liberal premise, which is that our personal experience is fine, whatever it is, so long as it isn't imposed on others.
Now, in this case there is some real reason to say it is being imposed on others. But in society at large, people are not willing to make the leap from that to say, the way this person has been formed by their culture, their sexual experience, their beliefs, is unhealthy to them and society at large. They don't want to say, actually, we should not encourage people to be turned on by x, y, or z. Not only might it impact others badly, it is bad for those individuals in terms of mental health, how they relate to others, etc. Because we don't want to put a moral spin on it, that's anti-liberal. People have to decide what is a healthy sexuality themselves, and we are very uncomfortable talking about a moral sexuality at all.
I would say, a sexual life that revolves around pretend violence, or even fantasy life that revolves around it, is not healthy. Not only because one day it might affect others, but because it is not good for the individual, it affects how they think and feel about other people. Maybe only a little, sometimes, but maybe not. People should try and avoid thinking that way, and while it's human to fail at times we can avoid exposing ourselves to thinks that make it harder.
But that's a very illiberal view on my part.