The activist Hassan Shaheen was captured in the same video, bleeding from the head as a soldier stomped on his chest. But this spring he helped lead the petition drive asking the military to remove Mr. Morsi. And he joined in the rejection of Mr. Maher, saying that by calling the ouster of Mr. Morsi a “coup” he was “following the rhetoric of the Muslim Brotherhood.”

“We will stand together, the people and the military, in the face of terrorism,” Mr. Shaheen wrote in a Twitter message, arguing that the Brotherhood’s political party “must be dissolved and all its leaders must be arrested.”

“No negotiation, no reconciliation, no going back,” he added.

Hossam Bahgat, founder of the Egyptian Initiative for Personal Rights, said the liberals’ goal — an Egypt governed by an inclusive civilian democracy — appeared to be further away than when Mr. Mubarak fell. Now, he said, the old institutions and elites from the Mubarak era are emboldened to push for a full return of the old order. “There is a powerful and well-resourced player now trying to push Egypt back to 2010,” he said.

Even those on the left who are critical of the military overthrow fault Mr. Morsi and the Brotherhood for their actions in power, for excluding other groups from decision-making, accusing critics of treason and exploiting religion as a political tool. They say that in recent days some Islamist leaders have told their supporters to prepare to use violence to defend Mr. Morsi, as they did during a crisis in December.

Brotherhood leaders say their organization has not condoned violence in Egypt since the days of British rule. They say private media outlets have worked for months to stir up nationalist sentiment against them, for example by circulating false rumors that they were considering giving away Sinai or selling the Suez Canal. Over the last week, many news outlets have claimed that Brotherhood leaders invited foreign interference by appealing for help from Washington to hold off the military takeover. Television hosts even assert that the crowds at pro-Morsi rallies are actually full of Syrians and Palestinians.

The military has set the mood as well. Before the takeover, it broadcast aerial images of the protests against Mr. Morsi, set to soaring martial music. On Sunday, it released another 30-minute broadcast depicting soldiers protecting the public, set to a similar score.

State and private television channels also broadcast images of Gen. Abdul-Fattah el-Sisi in his trademark black beret, explaining to admiring soldiers the military’s obligation to intervene in the national interest. “Egypt is the mother of the world, and Egypt will be as great as the world,” he declared.