Earlier quoted context omitted.
But the boycotts are rational, because even the Chinese government thinks that the developers are overextended and may fail. They seem to be taking the most careful, benign option.
boycotting a mortgage on a secured loan with 40% down is a political statement, not economically rational. The numbers are probably minuscule and the “boycott erase story” is itself mostly political.
It's perfectly economically rational if your equity is less than zero, which can happen when you put 50% down. It just means your valuation of the asset dropped in half.