Final answer:
Roger Williams's views on religious freedom, the separation of church and state, and fair treatment of Native Americans were controversial to the Puritans in Massachusetts Bay Colony because they challenged their rigid ideals. His beliefs led to the founding of Rhode Island, which was a haven for those seeking tolerance.
Step-by-step explanation:
Roger Williams's views were controversial for the Puritans in the Massachusetts Bay Colony primarily because he advocated for ideas that starkly contrasted with the rigid Puritan ideology. Williams questioned the Puritans' taking of Native American land without proper compensation, which was a direct challenge to the Colony's expansion efforts. Moreover, he argued for a complete separation from the Church of England and believed that the state should not have the authority to punish individuals for their beliefs, promoting religious freedom and the separation of church and state. These beliefs were deemed dangerous at the time since the Puritan society structured itself around a close relationship between civil order and religious practice. Williams’s advocacy for religious tolerance, including his acceptance of different sects except for Quakers, posed a threat to the Puritan's uniform community. His founding of Rhode Island as a haven for religious diversity and his progressive relationships with Native Americans further amplified the controversy.