I agree with Serp. For all of Scarfo's faults, it seems he cared about the rules and traditions. Plus, Testa was his friend, wasn't he?
Didn't he whack off his Nephew or something? Or was it Testa's son, I don't remember but they made a huge deal about it in the documentary, how he could kill someone who was like a son to him. And friendship doesn't mean to much in that life.