Well, I read more of the posts.
As an Instructor, and avid diver, a few points to consider:
First, YOU are responsible for YOU. I get tired of people asking me "why" they have to know self-rescue procedures when they'll "always dive with a guide". Simple fact, that everyone needs to remember, re-read, and memorize as a chant is that you must dive within your abilities and the conditions.
Second, the standard drill is to sign an indemnity agreement when you take a class, go out on a boat, etc. While attorney's often try and legally "pierce" these agreements, the plain and simple fact is that DM's/DiveCon's on boats have no idea what a person's skill level is, have no idea what their physical condition is, have no idea really about anything about a person other than the C-card and what the person might tell the proprietor of the establishment when they sign up for the trip.
Third, in discussions with fellow divers around the world, I am horrified when I hear people do not practice their safety skills on their dives. In not practicing these skills, they are doing not only themselves a disservice, but they are needlessly endangering their buddy. It takes only a moment to go over, prior to a dive, a quick review of buddy-breathing, or an air-sharing ascent, etc. Once in the water, everyone should make it a habit to take off their mask and replace it (yes, at depth), as well as BC removal. Finally, you should know where your buddy's weight system release is located....is it integrated, or not? If so, how is it released? Where is their power inflator button? Are they using an AirSource-type setup, an I3 with no hose, or what? Find out, please!!!
Okay, so I'm preaching. But everyone should know how to fix a problem at depth. In order to lessen panic, we all have to continually practice this stuff, so when something happens in real life (and if you dive enough, you will have incidents arise), you will find your practice and training will allow you to handle the problems at depth with little or no stress.
We can all speculate what happened to this young man. Unfortunately, statistics show that the majority of diver drowings occur with the weight belt still on. When students ask why we practice ditching weights and orally inflating the BC, they may not understand that it may save their life someday, but they will remember that their (inflated) BC is their friend.
So I have preached enough. Please don't become a statistic by thinking you don't "have" to practice the drills you were taught in your classes. All of these skills weren't taught to fill up class time, but for a very real reason.