This interesting article might explain their willingness to accept Sasso.
"SMM modelled themselves on the Italian mafia, although you can’t compare their power. Street crews and their petty beefs are very different from major organized crime and the Bloods are nowhere near as powerful as the mafia, although they are more prevalent. But Pistol Pete and the others had a fascination for Italian organized crime. They saw it as being very glamorous, but also a poke in the eye of authority. Yet street crews like SMM were more dangerous than the mafia in a way, because they were so much quicker to shoot. Personal slights would escalate into a murder. If the mafia rubs anyone out, it’s generally about money or business. With SMM it would take nothing"
https://www.vice.com/en/article/mbx48a/who-was-pistol-pete-sex-money-murder-nyc-bronx