Think about it... These are "leftists" we're talking about, so "left-justified" might be some sort of walking pun for them. Also, their slacker audience feels awkward all the time, so they probably decided to capitalize (AAAAHHHH!!!! DON'T USE THAT WORD!!!!!) on this trend rather than hide it behind the thin veneer of using attractive models.
No, the one thing I really don't get - and I guess this is more of a "casting director" kind of query - is "Why in the name of all that's politically expedient, would you use as a T-Shirt model a man who (I guess?) has a tattoo of intestines on his arm???"
No - don't answer that - there are some things which should remain a mystery.