the problem with transparency is we get to see how ugly we are.
and that offends a lot of people. a lot of people would very much rather be ignorant and very much champion such suppression of dissent and difference.
my read on a lot of the 'controversial' subreddits is that most people don't really care if anyone jerks it off to dead bodies, they just don't want to know that it exists. sort of like the homeless. people generally don't care about them, and their objection is primary that they have to see them and acknowledge their existence. they want them to 'go away' because they serve as a vivid remember of their own fragility and capacity for 'badness'.