In fact, advocates for rent control have taken Econ 101 (most of them), but they just disagree on how large the positive and negative impacts are. The purpose of economics should be to help us think clearly about the matter--for instance by identifying the potential empirical data that could adjudicate between competing arguments--but in its textbook form it is a ritualistic way of curtailing thought.
Beggs had merely cited the IGM poll of economists on rent control, which asked nearly 40 economists from Acemoglu to Zingales and found that all of them disagree with the proposition that "have had a positive impact over the past three decades on the amount and quality of broadly affordable rental housing in cities that have used them." Obviously, she needs to defer to the greater wisdom of Peter Dorman. Shame on her.