The point is that the FBI after Valachi say that La Cosa Nostra is a real organization,Hoover that since then ever said that the mob is a myth,used al the systems to destroy Cosa Nostra.

So sent in prison Tolomeo e other 3 innocent mobster,and used Bulger for destroy the Patriarca family.

That Bulger was a killer,drug dealer ecc wasn't important,everything for destroy the mafia.

the end justifies the means as said Machiavelli