See, the DM is the final word. An argument between players is always worse then simply just asking the DM to have a word if he agrees with what you're saying. If he doesn't, then you're going to have to put up with it.
He agrees. He was the one who brought it up in the first place.
Why don't you hand the sexual deviant over to the police in-character. Or, you know, just fuckin' kill him. Is your character really the type that would sit idly by while sexual abuse occurs?
Well, let's see. We'd just seen a bunch of people and animals sacrificed to an enormous tentacle-monster-god in order to get our ship safe passage, the ship was sabotaged from someone onboard unbeknownst to us so the shields went down, and then we had a big fuckin' fight that involved the destruction of five enemy airplanes, various people being squished into goop on the decks, and my accidentally half-killing the captain of the ship with a railgun. I was down to 1 HP, having until about a week ago done nothing more dangerous than send graduate students scathing emails and generally being a deadbeat, and went down to the hold to get very, very drunk. This was instead of doing something useful such as, say, repairing the shields or the command console, both of which I would have been able to do better than anyone else on board (I'm playing a glass cannon across the field, so almost no resolve, composure, stamina, etc., and I'd exhausted all available reserves of willpower by continuing to man the railgun after having been nearly killed by enemy aircraft).
Then I came up and he was molesting the prisoner who had been brainwashed to sabotage us. I managed to get him to stop, but perhaps you understand why she wasn't as focused on the molestation after everything else.
So yeah, I'm going to figure out what to do before the next session, but I was kind of distracted. There's one other character (who wasn't even here this session!) and we haven't exactly done that whole gelling-as-a-team thing just yet.