The film text itself contains this sentiment. At one point a brother denies that a gift to his sister is generous by claiming that his motive is selfish: he is happy when he sees his sister happy. Too bad this voice from beyond, the bearer of this genuine insight about ethics, must be slaughtered for the others to be capable of self-respect.
If the film strives to affirm the value of living for oneself, it fails because it portrays autonomy as based in ridiculous violence. If it suggests that love and desire are only possible in constraint, then it's completely corrupt because it fails to differentiate the two. If instead it wishes to punish us for being capable of these tendencies, if it seeks to reveal the logic of our own deeply destructive habits, then it succeeds marvelously but the message must be dredged up with more effort than it would take to have fun being a member of the Recchi family.