Maybe cuz they are thinking, irrationally i may add, that "if he didn't come here, this wouldn't happen, beloved Prince Zeth won't be in the frontlines", "if he wasn't being protected, the wolf would still be alive today" basically barking at the wrong tree.
Forgetting that 1. Their king is the one who asked for marriage alliance
2. The war is already brewing before the marriage happened.
3. Zaklak is the one actually responsible for the killing and progressing the war faster
It doesn't help that they don't know Louie or bothered to know him(the only ones thinking highly of him is the nephew, Zeth, Yullur, and the wolves) They have this prejudiced thinking of him. "Why is he here?", "Beloved Prince Zeth deserves a White Heart or anyone from this kingdom", they don't approve of the marriage because "Zeth belongs to Yullur and vice versa"(probably in their minds Louie the the "homewrecker"), also this weird warped idea of the their king (maybe) and their kingdom they think it's perfect when it's not (the forced marriages because honoring the history, based on the previous work with the same universe, and the princes doesn't think highly of their father, etc)
Tldr: the ppl of the wolf kingdom are thinking irrationally paired with warped idea of their own kingdom and history, and prejudiced of people of the other kingdom. They also don't like Louie too simply cuz Zeth and Yullur didn't get married instead.
I like the points Hashi is making this chapter but it's still pissing me off how people keep saying that Louie "caused" the situation. If we're talking literally, Azlak did. And, indirectly, even if he hadn't, the war would have happened anyway considering the political situation.
Louie is, at most, an ignorant sacrificial pawn and collateral damage. What the fuck kind of power do they see him having in this situation ?