

This person is a horrible, orientalizing racist, but “Islamism” in this context is basically a shorthand for “Islamic theocracy,” isn’t not just a confused way of saying “Muslim.”
https://en.wikipedia.org/wiki/Islamism
So ISIS, for example, are extremely Islamist, and the Taliban are as well. That is much less true of the overall factions opposing Israel in relation to the genocide, though they will inevitably have members and segments who are straightforwardly Islamist (as you have in most militant movements with mostly-very-religious membership).
(“Christianism” is sometimes used in the corresponding way, though it has other terms like christo-fascism or Catholicism to refer to it by depending on the specifics).
You can see people use the term that way if you put it into a search engine. I was just noting that specific word because the person I was responding to proposed it as a hypothetical nonsense word while they were misunderstanding what Islamism was.