When you tell them "Don't do that HERE", or "NOW", and say, "Do that in your room, it's encouragement."I am not encouraging my boys to go off and do anything,
You wanted to know how I made the leap to a vibrator, I think its a pretty straight line. Instead of saying, "don't play with yourself", you're saying "keep it in your room". There's a difference between understanding that something is going to occur, and sending a message to go ahead and do it. So if you're saying, "Hey, its cool. Go do your thing in your room" to a 7 year old, it would not be surprising at all if your older daughter asked you for a vibrator and you said, sure. "Just keep it in your room"
And I'm glad you noted that you are NOT one to say, "Well, they're gonna drink anyway. Better to do it under my roof", because to me, that's the same line of thinking.
And what's even more strange to me about this whole thing is that you're a woman. I cannot imagine the level to which I'd be horrified if my mother caught me spanking it or wanted to talk about it. I think kids figure that out just fine on their own.