The answer to that hypothetical student is: "You didn't engage in those same actions that your ancestors did; so, if you choose to feel any shame for their actions, then that's entirely on you."

Who gets to determine what are the "settled facts" about an umbrella term such as "racial oppression," Tim? You are being intellectually-dishonest, here. Debates over what constitutes racism -- be it policy, behavior, or unconscious bias -- is still widely open for debate on multiple sides, whether you like it or not. The fact that there is a lack of consensus on whether specific actions can be considered racist should suggest that "both sides" (or, more accurately, "two or more sides") is a valid reality to acknowledge.