What about those Tor sites that were recently busted. Yes, the content was far worse, but if we argue that usage of a site can be bad enough to warrant a loss in deserving your privacy protected, the difference between the two becomes only a difference in determining what is 'bad enough' and the argument you presented, that it doesn't matter since privacy should be protected anyways, no longer applies (as the people who are arguing it 'serves them right' are disagreeing with you only in terms that the content of this site is bad enough to warrant the same loss of any rights to site usage privacy).
Please note I am not saying the content of the two sites are equal. I am only saying that the wrongness/harmfulness of the content (which is clearly different) isn't taken into account by the point presented here.