When Isis say “polytheists” they don’t just mean Christians , they mean Shia Muslims as well because we believe in the holiness of certain people even beyond death and we visit their burial shrines in pilgrimage which is looked at as pagan.

https://www.jihadwatch.org/2021/04/isis-branches-out-into-comedy-accuses-pope-woke-i-of-trying-to-start-new-crusade