This is why you don't buy shit that has Mao's face or slogans, or Che's, or Stalin's. If you are not a card-carrying Communist who's willing to back up the rhetoric with real, violent dissent (in which case I probably don't want to know you, because you're scary), realize that people who come to power (and believe the only way to effective change is) through violent change have violent histories, histories which are not really all that far back in the past and which people feel very strongly about. Even putting the Peruvian Maoists aside, Mao is not the kinda dude you wanna put on a shirt. It's literally like putting Hitler or Stalin (though Mao might have killed more than both of those men through his policies) on your shirt and being all, "Hey, it's ok, it's ironic!"
No, it's not. And you're a terrible person. Every time you put that shirt on, a puppy gets its ears crushed by an automatic rice picking machine.
I say this as an individual who owns a shirt which has a sickle and hammer on it (which gets some interesting reactions from Asians and Eastern Europeans), but at least my shirt doesn't have a quote from Stalin saying, "Who needs Bolsheviks?" or something along those lines.