Much will be made of the immorality of Trump’s position, how he has abdicated the role of leader of the free world, and why his stance makes violence more likely. That is all true—but Trump’s stance is even worse than it appears.

The Hong Kong crisis comes at a particularly sensitive moment in U.S.-China relations. Competition between the two global powers may be inevitable, but its scope and intensity depends on the decisions both countries make. In Hong Kong, Xi faces a crucial choice—a 21st-century version of the Tiananmen Square crackdown would make a new Cold War all but inevitable.

A violent crackdown would make it much more difficult to calibrate competition with China. China will have revealed itself to be a totalitarian dictatorship guilty of the excesses associated with such regimes. Cooperation will become difficult, if not impossible, even on matters of mutual interest. Having crossed the Rubicon and incurred the costs, Xi may be even more willing to flex China’s muscles in the South China Sea and East China Sea, increasing tensions with its neighbors and the United States. If China handles Hong Kong in a heavy-handed way, that would also have repercussions for Taiwan, which would see its suspicions of the mainland confirmed.