This is one of the definitions from the OED:
a. To lower in character or quality; to debase.
1652 T. Froysell Gale of Opportunity Ep. Ded. sig. A3 At this news the proud Ruffler is sodainly dismounted, and his courage degraded.
1755 Johnson Dict. Eng. Lang. Degrade..to reduce from a higher to a lower state, with respect to qualities.
1762 O. Goldsmith Citizen of World II. 213 How low avarice can degrade human nature.
1784 A. Smith Inq. Wealth of Nations (ed. 3) II. iv. viii. 500 English wool cannot be even so mixed with Spanish wool as to enter into the composition without spoiling and degrading, in some degree, the fabric of the cloth.
1857 C. Kingsley Two Years Ago III. vii. 201 So will an unhealthy craving degrade a man.
1875 B. Jowett in tr. Plato Dialogues (ed. 2) V. 41 This custom has been the ruin of the poets, and has degraded the theatre.