First, I think FB's thread is very important. The answer to his question will often be a definite "NO." Life is more complicated than black and white, so depending on the circumstances, it is possible a victim and perpetrator could reach a level of understanding that could facilitate a better or even "good" relationship.
You listed several criteria that you used to make your case and I really have nothing else to add---except that a common theme between you and FB seems to be the young age of the perp. I can certainly see where an older--older than 19 or 20 year old could mature and change under some circumstances. I think a lack of violent behavior is key while acknowledging that behavior of the sort we're talking about is inappropriate under any circumstances.
The age differential between you and your brother in law is similar to the one between my perp and me(13 and 19). The guy who abused me was not family and he was violent. What started out as somewhat consensual playing around(but not really given the ages) turned violent and degrading when I didn't want to do what he asked. I could never forgive what happened. I'm thankful I don't have to share the same house, street, or town with him. That would be another layer to get through---and there's enough depth to this already.