It's so strange to me that a culture would encourage people to remain silent during something like this. I can't imagine having a stranger put their hands down my pants on a crowded subway and not turning around and slugging them in the face.
Regarding a culture encouraging people to remain silent during something like this, hard for me to think of a culture that DOESN'T encourage somebody to remain silent about being sexually assaulted, although Japan does seem to have a unique problem here.