Does my statement: "What is wrong with these professors who love to delay us from prayer?" constitute backbiting against my professor, knowing that he delays us from Friday prayer, and in his class, he condones usurious loans, drinking alcohol, and the immodest display of female students?

Backbiting is forbidden, but it is permissible to mention a transgressor in a way that displeases him, without aggression. One who openly commits sins, such as intentionally delaying students from prayer, or condoning usury, alcohol, and immodest display, is considered a wicked person (fasiq), and there is no backbiting in mentioning him for what he has openly committed. It is permissible to expose him so that people may beware of him. Intentionally delaying students from prayer is a crime that warrants punishment and censure. If your statement is limited to the professor's open commission of the aforementioned transgressions, then there is no blame upon you. If the professor condones major sins by deeming them permissible, this is a major act of disbelief (kufr akbar) that expels one from the fold of Islam.