And it's stance on slavery: "There shall never be any bond slaverie, villinage or Captivitie amongst us unles it be lawfull Captives taken in just warres, and such strangers as willingly selle themselves or are sold to us. And these shall have all the liberties and Christian usages which the law of god established in Israel concerning such persons doeth morally require. This exempts none from servitude who shall be Judged thereto by Authoritie."
The Constituion of Massachusetts (1780) also banned slavery.
This is inconsistent with your characterization of the Puritans.