Joe's behaviour is completely unacceptable. Her treatment at work like some leper again is unacceptable though some this could be attributed to awkwardness on how to broach the subject or if it should be talked about at all.
Two things strike me though:
Shots off of Justine's stomach. The best response I have heard from a girl in a mixed group when asked to do it was "I will do it if you do it first." It turns it from another girl doing shots on the bar to a weird group activity which is silly, not sexual. Obviously a straight up no would suffice, who cares what a drunk person says?
The second thing was how it went down. During a recent stag do a random girl walked over to one of our group and kissed him randomly without warning or anything. The guy pushed her away, recoiled in horror and said with a look of despair "she - put - her - tongue - in - my - mouth!?"
We laughed but seriously, we knew it wasn't consensual, if she went back in we would have pulled her away.
I feel this is the correct response to being jumped on. This or a loud no.
Not reciprocating, then questioning whether the wife would mind is not a no. Standing there awkwardly waiting for it to be over does not convey stop and it doesn't give friends an opportunity to come to the rescue.
Without a no the lack of participation can suggest hesitation. Asking about the wife perhaps reinforces this. "Oh so thats why you are slow getting into it. Don't worry about her." From the outside the lack of no and look of awkwardness could suggest this isn't something you do very often. Not that you want it to stop.
Justine is not at fault in the slightest. Joe forced himself on her. That said I wonder how differently things would have been if she straight up said no or even pushed him away.