Why does winthrop use an analogy to the status of women within the family to explain his understanding liberty?

He felt that moral liberty, in its most perfect form, was the liberty to only undertake good works and deeds. He likened it to a woman choosing her husband: in general, making a decision. In both instances (woman obeying her husband and a person obeying moral and just laws), Winthrop felt that it was a moral duty.