I sincerely doubt that they are any way near that yet! But for that reason I find this action ok.
I think that thing a great idea, in that it would never harm anyone by mistake. But I wonder if it hurts enough for the victim to get away? If the attacker is trapped inside, you could have a very dangerous situation, and what if there is more than one which seems to be the mode in many places?I was reminded of this article from four years ago, which was also hailed, and condemned, by many. Like the knife, it's not a perfect solution, but it does give the victim a choice she doesn't have without it. And who knows? If enough rapists manage to get their dicks shredded, or removed, maybe the authorities will finally enact REAL laws protecting the victims of these crimes. And enforcing them!
Until then, I'm on the side of the women. Protect yourself however you can. And then report the attack.
However, I realize - a bit unexpectedly - that I am all for the idea of self defense in a quite violent way, especially in countries where the problem is widespread. Talking about does not seem to have much effect. But - will it just make it worse, or will it make it stop??