Are the Abayudaya Jewish?
Are the Pashtun, who are Pashtun while referring to themselves as “B’ni Israel” both a little bit Jewish and Muslim?
There are ethnic elements in the invention, uptake, and adaptation of Islam that may not be separated from “Muslim” — not “Islamic” — self-concept and volunteered description. When for tribal business, independence, security, or survival one civilization accepts the overlay of another, it becomes difficult in time to pry apart that melding. At the same time, an ethos that drives against the grain of humanity, i.e., as that possessed by the “Islamists”, needs must be ejected at least in part.
There is an argument to be had about the character of Muhammad and that of Islam with some who would put all Muslims in the al-Qaeda (or similar) box even though Muslims appears the first victims (and warriors against) that efflorescent fascism that has no place among good people.
We are born with our identities: culture and its customs and laws, our parents, and our families, our names. God (Nature and the Universe) provide us with no choice in those earliest matters. However, as we are not fixed as characters in books and much less in place and time, we as adults may confirm our cultural self-concept or change it. Over time, change is what we do because “back there” in time includes ideas and practices that become for each “new world” — a generational concept — maladapted.