Your interpretation of turn the other cheek is incorrect. It wasn’t meant as instruction to let someone walk over you as your definition implies, but rather as instruction to not take vengeance or revenge into one’s own hands.
It also brings up the issue that, striking someone deemed to be of a lower class with the back of the hand was used to assert authority and dominance. If the persecuted person "turned the other cheek," the discipliner was faced with a dilemma. The left hand was used for unclean purposes, so a back-hand strike on the opposite cheek would not be performed. The other alternative would be a slap with the open hand as a challenge or to punch the person, but this was seen as a statement of equality. Thus, they argue, by turning the other cheek the persecuted was in effect demanding equality.