But someone introduced it to you. That makes it different. If they had not exposed you to it then the odds are great that as a child you would not have participated. To me, that puts the "willing participant" part in question.

Yes, this kind of stuff self perpetuates, that doesn't excuse you but at least should give you a starting place to find forgiveness for your young self. There are extenuating circumstances that have to be viewed and explored. Start at the beginning, not the middle, not the end. Start where it started with you.