Whether it's right, wrong, or indifferent, as coaches, we're responsible for what happens on our watch and that's been the case for a long time; not a new ideal. Same is true for teachers, parents, or anyone in a leadership position or position of power. I am also of the mindset that if someone wants to do something, they will find a way; supervised or not. Last time I checked people still break out of prisons, despite being the most supervised areas in the world. So, I don't necessarily feel it's right for coaches/leaders to be held responsible if they didn't know, but again, it comes with the territory and we all know that. You can disagree but it's the truth.
I have never had to deal with hazing while a HS coach but in college, we had to address it at every beginning of the season meeting cause the school had an issue with a "talent show" that had been going on for years, and one kid, one year, got his feelings hurt cause a picture of him deepthroating a hotdog was sent to the wireless printers around campus. He was a freshman and probably 90% of campus wouldn't have ever known who he was, but, that's the world we live in. Boys will be boys but they better know there are consequences now for their actions.