I think the psychoanalyst’s counterargument is that what is or is not fun is shaped by the same social forces that shape all preference, and that therefore, something being enjoyable cannot be extracted from the same motivating factors as other actions.

I’m not a psychoanalyst, though, so I’ll acknowledge that ‘it makes my brain release lots of endorphins’ is at least partially a justification in and of itself, and that kink tends to involve actions that create very large spikes in endorphins even in comparison to vanilla sex, so there’s definitely an element of ‘it just feels good’ (where ‘feels good’ isn’t necessarily invoking pleasure, merely some pleasant experience) that needs to be acknowledged. What is interesting about that to me is that it means that we build a lot of social constructs that abut behaviors that ‘just feel good’, and, as a result, those social constructs tend to be very instructive w/r/t the relationship between broader social behavior and more instinctively hedonistic behavior. Therefore, the socialization and society of kink become the place where we can try to rectify the confounding inputs.