On Thursday morning, the chief executive of what is perhaps the world’s most popular social app went before Congress. Like so many social media CEOs before him, Shou Zi Chew’s mission was to persuade skeptical lawmakers that his company, TikTok, operates responsibly and within the bounds of the law. In the face of doubts and outright hostility, Chew would have to remain calm and genial, attempting to make his case while in the straitjacket of Congress’ hearing format: an hours-long…