As we all know, this is a phrase that the Terminator (portrayed by actor/bodybuilder/now California governor Arnold Schwarzenegger) picks up during a street fight to get some clothes. He uses it later on a custodian who's collecting trash from the hotel rooms.
Here's some dialog from the 1984 movie "The Terminator":
Somebody who is an ASSHOLE but chooses wisely on who their targets are, usually somebody who brings it upon themselves. Selective Assholes are always nice unless your an ASSHOLE or justplain 'ol have it coming for you. Selective Assholism is usually executed through sarcasm often it is hard to tell if the Selective Asshole is being nice or not.
"Man the guy is an Asshole"
"Nah fam, he's a selective asshole that dude deserved it."