Unfortunately not about Fremen but still great series.
“The opposite of Fremenism is almost invariably termed ‘decadence.’ This is the reserve side of this reductive view of history: not only do hard conditions make for superior people, but that ‘soft’ conditions, associated with complex societies, wealth and book-reading weenies (read: literacy) make for morally inferior people who are consequently worse at fighting. Because we all know that moral purity makes you better at fighting, right? (My non-existent editor would like me to make clear that I am being sarcastic here, and it is extraordinarily obvious that moral virtue does not always lead to battlefield success.)”
https://acoup.blog/2020/01/17/collections-the-fremen-mirage-part-i-war-at-the-dawn-of-civilization/