I think Vito and Michael used violence to protect people from the violence and discrimination they faced in the country. The state did not want to take care of them so they had to build a state of their own where they were the kings. This is exactly what the opening scene of the Godfather says and explains why the institution is kept alive and cherished by people who are regularly treated as second class citizens, and could not have good and honest lives even when they tried. The story is well written. Was it true in real life? That is another question.