On Seat Mates Who Read Girlie Magazines

Never have I woken up and wished to be seated next to a man reading porn on a train.  Evidently, and I'm learning this the hard way, not wishing for something specific has nothing to do with the universe and it's ... sense of humor? ...

As in, just because you don't want it doesn't mean you won't get it.

My seat mate is reading porn.  A girlie magazine.  There are photos.  There are cartoon descriptions of kinkiness. 

Porn in your bedroom?  Fine. 
Porn in public?  On the train?  Next to me?  Not fine. 

Do I say something? 
What would I say? 
"Is that interesting?"
"Do you have a hard-on?"
"How much does a magazine like this cost?"
"What's the attraction?"  Scratch that.  I'd have to add "other than the obvious" and dumb questions usually get dumb answers.

Do I get to say something?
Just because in my world it's in poor taste to look at naked women on a crowded train does not mean it is in Japan.  Whose morals rule in such a case?  Japan is not my country.  He's Japanese, I'm a foreigner.  Japanese social norms trump my definition of public decency.  Right?  Really?

What if I read it with him?  Is that being passive-aggressive?  If that were the case, would that be so bad? 

What if I--oh, I'm so sorry--spill coffee on his magazine when I reach for the cup from the young food-selling woman?  Is that kind of passive-aggressive behavior better?  It's certainly less passive and more aggressive.

What if I break the rules and make a phone call in Japanese right here, right now?  I'm supposed to go stand on the deck to take or make calls.  Sorry.  Dumb foreigner.  I don't know the rules.  Do I dare?  Then again, if he knew I could read what he was reading would that change his mind?  Would he care?

So far I have no answers.  Perhaps by the time he gets through to the end I'll have thought up some witty and biting comment that may or may not make him think.  I'm open for suggestions.