Supposedly this quote makes Schäuble the official spokesperson for multiculturalism. But Schäuble didn't actually say Islam is part of Germany. He said Germany has an interest in saying so. In a recent interview he said it was a mistake for Germany to bring in so many Turkish workers since they did not integrate as expected, and the problems have increased with the third generation.
Via the Local:
Finance Minister Wolfgang Schäuble on Tuesday warned Germany must not discriminate against its Muslim population, saying that Islam was a part of its society. His comments contrast starkly with those of the country's new conservative interior minister.
“We have every interest in saying that Islam is a part of our country and in inviting Muslims to value what we have achieved in the Western World,” the Christian Democrat told the latest edition of political magazine Cicero.
Religion, faith, democracy and universal human rights are all compatible, he added.(source)
