When you see someone appealing to "common sense" when defending prejudice/bigotry, they're encouraging people to suspend thought or criticism that might challenge prejudice, and instead, retreat unthinkingly to the comfortable inertia of the social norms which establish the prejudice in question.
"Common sense" is a thought-stopping phrase and concept. It is the same as saying, "Just go with cultural traditions which support prejudice and oppression because those are familiar and comfortable."