Final answer:
Prince John refuses to stop the tournament in Ivanhoe to assert authority and demonstrate his disregard for chivalry, illustrating his ambition for power and political maneuvering.
Step-by-step explanation:
In Ivanhoe, Prince John refuses to stop the tournament despite the odds against the Disinherited Knight because of his desire to assert his authority and demonstrate his indifference to the chivalric code which would normally compel a leader to ensure fairness. Prince John's actions reflect his contentious claim to the throne, his ambition for power, and his disregard for the traditional values upheld by the nobility and chivalry of the time. His decision to let the tournament proceed even under inequitable circumstances serves to emphasize his political maneuvering and his attempt to strengthen his position against his brother, King Richard.