How Muslim immigrants are not familiar with German culture

"is now host to up to a million asylum seekers, most from war-torn Muslim countries unfamiliar with its culture." What does that mean? That they come from cultures with groping of women are part of the culture? That they didn't know it was not part of the culture? Also, what about the fact the attackers included "but also three Germans and an American, among others, the report said."  Also, what does the invocation of culture here mean? Do Muslim cultures allow or condone sexual harassment and the public groping of women?  Sexual harassment is considered acceptable in "Muslim cultures"?