A two-member Tamarod delegation met with Germany's top diplomat late Wednesday to discuss the situation in Egypt.
"We told him that he had to respect the will of the Egyptian people, because the people – not ousted dictator Mohamed Morsi – will remain," Tamarod political officer Mohamed Abdel-Aziz, who attended the meeting along with group founder Mahmoud Badr, told Anadolu Agency.
"We told the minister that the Egyptian people took to the streets in a popular revolution on June 30, and that he must recognize the popular will," said Abdel-Aziz.
"We also told him that we reject any talk of a safe exit," he added. "There must be fair trials for Muslim Brotherhood leaders, who are involved in terrorism and violence."
Asked about whether the talks included the possibility of releasing the detained former president, Abdel-Aziz said the issue had not been discussed.
He added that the German foreign minister had affirmed his support for democracy.
"The Egyptians must express their opinions through democratic elections," Westerwelle said.
Germany, he added, "does not want to interfere in Egypt's internal affairs and respects the will of the Egyptian people in their transition to democracy."
Badr, for his part, said that he had "told the minister that they were upset about some of his remarks, in which he had called for the ousted president's reinstatement."
"I asked him why you rejected (Adolf) Hitler in Germany, while you want him back to rule Egypt," Badr wrote on his Facebook account.
"We told him that we want a clear recognition of the Egyptian will in order to remain respectful of the Germans," he added.
Westerwelle arrived in Cairo on Wednesday for his first visit to Egypt since Morsi's overthrow.
He is scheduled to meet with interim President Adly Mansour, Vice-President Mohamed ElBaradei, Defense Minister Abdel-Fattah al-Sisi, Arab League Secretary-General Nabil al-Arabi and leaders of the Muslim Brotherhood.