Would this be the same mentally disturbed six year old who was sent to the Principal's office, then smashed a picture on the principal's desk and then used the hunk of glass as a weapon to first try to hurt the principal before turning it on himself? I would have to question you -- what would you do? Would you let the child potentially hurt themselves significantly, or attempt to grab a hunk of glass fron the child -- knowing the odds of deeply slashing your hands or his hands are very significant, or would you shoot a set of taser probes at him to disable him from a safe distance?
Where I work, we keep an off duty police officer any time the building is open to the public. More and more, they're not only carrying their 9mm, they're also carrying a taser. This is especially true with the officers who regularly work the night shift. For their regular shifts outside our building, it's not just a matter of disabling the drunk who got into a bar fight -- it's safely controlling the guy hopped up on PCP, Coke or Meth who thinks he's Superman or the Incredible Hulk. Does getting hit with a taser hurt -- heck yes. Every muscle in your body goes rigid and it absolutely kicks your butt -- holding that taser on for a few seconds is like the most intense workout imaginable and you wind up exhausted. Are there dangers involved? Yes, but there are dangers involved with anything. A good shot with a collapsible baton can break a rib (and puncture a lung), pepper spray can do more to upset a dope head than stop them (along with anyone downwind), and I think we can all agree that putting a 9mm slug into them isn't going to go over too well...
Like everything there are risks involved. Sure, odds are that somewhere someone will one day get hit with a taser and die. Odds are that someone will die doing almost anything and everything. They die during or after riding a ride, they die during or after playing a sport, they die during or after yadda, yadda...