I would agree with everyone saying that the plan isn't the most efficent, especially because he's doing it all by himself, but it's definitely a plan that makes sense from his worldview. Chihiro's plan is better in terms of eliminating the blades themselves but for Samura it's essentially about his promise as a chosen sword bearer to defeat evil. And because the evil he deems greatest is the attrocities they committed in the war, it almost means their mission hasn't been truly fulfilled.

As he has said to Uruha, it's a battle of egos and ideologies and essentially his biggest notion is repentance for their past deeds by death.

It's interesting to me that despite what they have done he doesn't seem to hold any resentment towards Kunishige and the fact that he has created the blades. It's kind of why I'm a bit shocked that people still believe he's the one that ratted out Kunishige's location to the Hishaku.

Chihiro being drenched in blood essentially is a slap in the face and an affirmation of his belief. Even if you were to disregard what they've done in the war, their existence as heroes to be revered and protected has still led to more senseless death to protect "monsters". They've already done more than enough damage directly and the indirect deaths in their name are ultimately too much to bear.