AOG - //And if one looks further in a dictionary one would find the use of the letters ist
-ist. a suffix of nouns, often corresponding to verbs ending in -ize or nouns ending in -ism, that denote a person who practices, is expert in, or is concerned with something, or holds certain principles, doctrines, etc.: apologist; machinist; novelist; socialist; Thomist.
And in other dictionaries
Cambridge Dictionary
Islamist:
/// a person who believes strongly in Islam, especially one who believes that Islam should influence political systems ///
Collins English Dictionary
/// An Islamist is someone who believes strongly in Islamic ideas and laws. ///
Seems to me that covers most who follow the Islamic faith. //
In modern media parlance, an Islamist is an extremist, and I think you know that as well as I do.
The word 'terrorist' is not confined to extremist Muslim fanatics, but such is the perceived connection, that when the media say 'terrorist', it is accepted that they mean ISID supporters, or similar fanatics, even though the strict definition of the term 'terrorist' is not limited to them.
Are we done with the semantics argument now?