You need to be smart about this, but there's plenty you could do with a simple complaint that your professor wastes class time to talk about irrelevant things.

If you are in the US or UK, you should remember to include that class time is paid at a premium rate by you or your parents.

Also tell them you do not feel that the material being delivered adequately prepares you for exams. Or the time spent on these comments could have been utilized for revision or new knowledge instead.

And that these kinds of rants create a hostile learning environment. Especially to people from countries targeted by your prof's rants (i.e. Chinese students). Also mention that your prof's empassioned attitude during these speeches makes you feel unsure about discussing the issue with him directly, since he might perceive you as an ideological enemy and make achieving your academic goals difficult for you (and then stress that you make your complaint anonymously for this reason).

Use a couple examples to demonstrate how his rant was irrelevant to the curicullum supposingly being delivered, and emphasize the time spent on these things.