I want to know the answer to the following question:
Who disagreed vocally about the demonstrations being permitted?
All the background I'm provided with is that "On September 10, 1987, after a lecture from hardliner Yegor Ligachev at the Politburo for allowing these two unsanctioned demonstrations in Moscow, Boris Yeltsin wrote a letter of resignation to Gorbachev, who had been holidaying on the Black Sea.". Is that enough to answer the question?
Answer: yes