You are exactly the target audience, and I'm excited you've seen the video. I can see why you might see it that way, but it's not what is really going on. Sure, some sharks are dangerous - which can be said of almost every predatory animal in the right setting. Of the 380+ species, most sharks never grow larger than about 4 ft and eat small fish and inverts. What you are talking about is the wrong image the media has fed the general public. That being said, NO sharks are targeting humans as a food source. Most shark bites are either people being stupid or mistaken ID by the sharks looking for food. Sharks aren't these mysterious killers cruising the oceans, and people need to see that. Shoot, of the 380 species, most people can't get much beyond naming bull, tiger, hammerhead, white, black tip and nurse because that is what they see on TV. Those are not a majority of sharks. It's like saying all Mustangs are fast. 90% of Mustangs are entry level small motor cars. But people are familiar with the loud, flashy fast ones - so they label all of them that way.
Don't fear them - understand them. These sharks are not being treated like a family's pet dog (although remember what pet dogs started off as). Inverting a shark is known as tonic immobility. It's a widely used method to safely handle a shark, and is now shown / proven to be something they also do in the wild on their own. I've done it from everything from bulls to hammerheads. I still have all ten fingers.
Sitting on a target/platform is not a negative thing in anyway. They line up on their own. They are not forced to stay there, and in fact can and will swim away if they want to. It shows the intelligence of these animals. They understand the benefits of interacting with the humans, and are there to do so on their own accord. In fact the ability to understand them enough to be able to use the natural behavior of lining up shows our advances in behavioral understanding as keepers.
Nurse sharks under human care are probably the #1 source of information we have for the biology of benthic sharks. That understanding is leading us to better understanding of the eco system and their roles in it. It also has lead to improved methods of habitat protection and restoration - which means healthier reefs, which translates directly to a healthier Earth.
Is it there for entertainment - in all honesty, entertainment is a side effect. It's set up for education and conservation. If you happen to walk away with a huge smile on your face after having the time of your life, so be it. I have dedicated my life to working with aquatic predators and educating people about them. I smile every time, and I love sharing that with anyone who wants to experience.