Wow... from how you say he responded initially (washing himself with Comet, vomiting, etc) - it sounds like this incident triggered feelings from something much further back. If he was ever victimized as a child then yes, a 100 pound woman could easily victimize him again.
I keep telling him he must have wanted it
Personally, I think this is the biggest disservice you can do him right now.
If he was victimized, and he keeps trying to see it from the vantage point that he wanted it - he'll never get the pieces to fit.
You love him - support him. Trust him. Believe him. And be there for him.
my 2 cents worth