How did Muhammad Ali demonstrate that principles matter in his life?

By contesting the laws of his country, to obey a higher law and his own moral conscience, while also fighting for equalities.

Explanation:

In Mohammed Ali's prime, while he was the undefeated heavyweight champion in boxing, he refused to be drafted into Army for Vietnam war in 1967, with the opportunity of multiplying his wealth by accepting an army job, instead, Mohammed Ali keeps advocating for civil rights, and to the extent that he risked everything he had laboured, trained and toiled for, at the peak of his boxing career, to defend the principles he believed in.

He also championed for the cause of black separatism and resistance to white dominance.