Islamophobia is a cover for racism, no doubt about that. Yes of course, Islam is not a religion and that Muslims can be of any race, but it's much more than that. The bulk of Muslims in the world are from three parts of the world: Africa, The Middle East and the Indian subcontinent. Those people make up at least 80% of Muslims, with the other 20% being orientals (East Asians) and white people (Chechns, Bosnians, Albanians, and converts).
So people who hate Arabs, blacks or the three nationalities of the Indian subcontinent, replace the race or ethnicity with the Muslim tag. And whenever they're caught out on their racism, they say, "but Islam is a religion not a race" and thus they have their prejudice covered.