But 50Shades, it is actually just a form of headcollar and stallion chain, a method of controlling extremely difficult horses that has been around for ages. A stallion chain is a chain looped over the nose or through the mouth of the horse, it is very easy to fit them badly. The halter you have linked to is actually designed with loops for the chain to sit in the correct position, hence less likely to cause damage in the wrong hands. The principle it uses is that of control and release - ie, the pressure is only applied when the horse misbehaves, and is released when the horse behaves again.
I worry about the fact that you claim to have used lots of controller headcollars yet don't seem to have much of a grasp of the kind of behaviour in a horse that really needs these. As I said, the right equipment in the wrong hands can do a lot of damage, whereas equipment designed for tricky horses in sympathetic hands can do a lot of good. I had a horse once (a 750kg youngster) who needed a good deal of explaining to why his behaviour was unacceptable - 17.3hh of big Irish Draught on his back legs doing his best Kevin the Teenager impression was a lot of horse above you! A few months with a control headcollar, and this horse was leadable by a child, and remained a thoroughly lovely horse the whole time I owned him. But stiff treatment was needed initially to get him going in the right direction in life.
There are many pieces of kit that, as you correctly say, can all be torture devices in the wrong hands, but I am unsure why you say you 'disagree that bad hands are worse' than bad kit. A snaffle fitted and applied incorrectly can cause discomfort and damage to a horse, a bitless bridle is not necessarily kinder than a bit, and the number of gags I see being used harshly makes me weep sometimes. You see white hairs on horses' tails and legs from bandages being fitted to tightly and left on for too long, horses with marks from spurs used by nagging legs, noses distorted by over-tight flash nosebands. In the show rig the Swales is super-fashionable right now, a horrific bit capable of real and serious damage, fine in the hands of an experienced rider on a strong horse, but the amateurs see them and put their own horses in them because XXX has a cob in one, etc. Ignorance plays the biggest part in damage to horses by harsh kit.
The problem of strong kit can be best summed up by thinking about schooling whips. How often do you see a rider schooling their horse, nag, nag, nagging away at their horse with constant little flicks of the whip, either because they don't realise they are doing it or because they lack the conviction to use it once and use it properly. The horse switches off the the gentle constant use of the whip, and is genuinely surprised when it is used to give a proper reminder that subtle use of the leg should be sufficient. It is the same with this headcollar - lead a horse around with it a bit tight, and it is both annoying and ineffective. It should only come into play when it is needed, and the signal should be clear and brief.
As for "That piece of equipment is in a child's hands!" you are right - it has no place in any childs' hands. The tiny picture you show, though, does not show the child, or their hands. Nor is it the picture Eskadron use for their advertising. They show a large grey horse, and advise that the equipment needs to be used with skill and consideration by the handler. They also sell replacement chain rings as the chain has safety links built in - unlike the good old-fashioned stallion chain!