Lots of good articles on Canadian brutality in WW1 if you do a search. As for war crimes in particular, here’s one of many articles mentioning how Canadians killed prisoners of war:
https://nationalpost.com/news/canada/the-forgotten-ferocity-of-canadas-soldiers-in-the-great-war
I believe that “Indian Giving” is sourced in a cultural misunderstanding between Indigenous and European societies. Indigenous societies were reciprocity based, so giving gifts should be reciprocated with a gift of like value to strengthen relationships, or increase honour (social standing). The Europeans were working in a patron-client system so a gift was seen as a way of purchasing access to power through a patron. The Europeans thought the Indigenous people were paying for access to power (like a tributary), so there’s no expectation of returning a like gift. The indigenous people thought they were entering into a mutual relationship, and when a like gift wasn’t returned that was seen as reneging, so they took back their ‘offer’.
Glad to have an anthropologist kick my ass.