My parents got me one of these when I was a kid.  I didn't like it.  I was a very passive boy and abhorred violence.  The idea that boys were expected to defend themselves when physically attacked really bothered me.  I knew I wasn't a fighter.  I felt shame and I lived in fear.  I didn't want to be hurt, but it seemed that being vulnerable meant you deserved abuse.  So what were my parents thinking when they bought me such a gift?  That's the trouble, they weren't thinking.  They simply went to the toy department and picked out something that was supposedly for small people with penises.