Rhode Island paid the Narragansetts for their land.
It was not theft.
https://en.wikipedia.org/wiki/Rhode_Island_Royal_Charter
The Rhode Island Royal Charter provided royal recognition to the Colony of Rhode Island and Providence Plantations, approved by England's King Charles II in July 1663. It outlined many freedoms for the inhabitants of Rhode Island and was the guiding document of the colony's government (and that of the state later) over a period of 180 years.
The charter contains unique provisions which make it significantly different from the charters granted to the other colonies. It gave the colonists freedom to elect their own governor and write their own laws, within very broad guidelines, and also stipulated that no person residing in Rhode Island could be "molested, punished, disquieted, or called in question for any differences in opinion in matters of religion".
The charter was not replaced until 1843, after serving for nearly two centuries as the guiding force of the colony and then the State of Rhode Island and Providence Plantations. Historian Thomas Bicknell described it as "the grandest instrument of human liberty ever constructed".[1]
The Royal Charter of 1663 confirmed everything that the Patent of 1643–1644 had given, and it granted power to the colony to make its own laws, guaranteed religious freedom, and did not require oaths of allegiance.[5]
Three points in the charter distinguish it from any other royal patent that had ever been granted.[5] It acknowledges Indian rights to the soil,[5] which was far different than the European doctrine of "possession by right of discovery" which was part of the "royal prerogative".[6] Historian Samuel G. Arnold writes that "Rhode Island was the first solemn protest"[6] against taking land from the Indians without payment. Roger Williams established this policy when he settled the colony by paying the Narragansetts for the land, and his views were maintained by those who followed him there.[7]
A second remarkable point in the charter is the rights of conscience that it extended to the Rhode Island colonists[7] which has become the "sole distinguishing feature of Rhode Island's history".[7] A third distinguishing point is its "democratic liberalism"[8] which allowed the Rhode Island colonists to elect their own officers and make their own laws, so long as they were not contrary to the laws of England. The provisions were very flexible, allowing the laws to consider "the nature and constitution of the place and people there".