Fate/Zero

[Ryllharu]

Mentioning that they are one of the original families means that they have fought in every war since its inception, so they know honor may not always be present. Even children's card game series don't pretend that everything is done honorably. Honor-bound combat isn't called an "ideal" for no reason.

Rin is a counter-example. We know that she gets raised believing all magi are great and wonderful. Of her father, she sees him making unicorns and stuff out of crystals, not burning her uncle alive. She doesn't yet realize how brutal things really are. Tokiomi is largely sheltering her. You'll note he had no such reservations about his other daughter.

If it was the 5th War, Iri would have left him tied up to the tree. Instead, with zero hesitation, she asked Maiya to kill him while she held him in place. Saber isn't a super-idealist because of how her reign ultimately went, so she wouldn't have objected to the killing itself, but shooting someone in the back while they are helpless is not the definition of honorable. However, Iri knew that was the only way they could stop Kirei (even if it ultimately failed).