It's not as if all CS classes have to use objective standards of grading.
It's also not the case that objective standards of grading can't be gamed.
It's also, also not the case that objective standards of grading exist beyond, say, multiple-choice exams, which are more or less useless for testing practical knowledge.
My confusion is more how one can disagree with someone in a CS class given that almost every issue is pretty objective.
Link.
Given the positive reactions, I think the professor seeded them with a positive impression of the site's content.