meaning of 身を切る

Question

This is a passage from Ｒｅ：ゼロから始める異世界生活 2 light novel. Subaru has finished telling Ram the Japanese story The Ogre who cried. story summary by Crunchyroll (link contains spoilers for the anime series)

Put simply, the story is of two friends who just happen to be ogres, one red and one blue. The red wishes to befriend the people of the nearby village, but they fear him and see his attempts to befriend them as tricks. The blue ogre comes up with a plan in which he pretends to attack the village, telling the red ogre to rush in and save the day by chasing him off. It works perfectly and the village welcomes the red ogre, who becomes very happy. After some time, the red ogre begins to wonder what became of the blue ogre, so he travels to his house and finds a letter left by the blue ogre, who has gone away so the village won't discover the two ogres friendship. Realizing his friend has left forever, the red ogre weeps.  

Ram is not happy with the behavior of Red and states her opinion plainly:

「……でもラムは、赤鬼の方が度し難いと思うわ

「自分の望みに青鬼を巻き込んで、結果、自分は何も失わずに青鬼に失わせただけ。ひどい結果があったものと、少なくともラムは思うわね」

「じゃあ、お前は鬼二人はどうすりゃよかったと思うんだ？」

「……赤鬼は、本気で人間と仲良くしたいと思っていたんなら、角でも折って人里へ下りればよかったのよ。青鬼が見ていられなくなる前に、身を切るべきだった」

I can’t quite figure out the exact meaning of 身を切る here. It seems to be used mainly in the figurative meaning of “cut (the body/flesh) like a knife”, e.g. (from EDICT)

身を切るよう - piercing (cold), biting (wind)

But here it looks to be used in the literal meaning? Is she saying “he should have cut his body (to cut off horns) before Blue had to leave”? Or is there some other interpretation I’m missing?

Answer 1

This looks like some intentional wordplay by the author that juxtaposes the usual figurative use (pay the price yourself) with the literal meaning (cut your body) since it's Oni we're talking about here and their horns symbolize their power/monstrousness and differentiate them from humans. So the answer to your question is "it's both."

Answer 2

I doubt that it is meant literally. To me it seems like an idiom meaning "explore other options" or maybe "take a little risk" The Red Ogre should have tried EVERYTHING, before involving the Blue Ogre and thereby losing his best friend.

...Apparently someone disagrees. So I'll try again. With its connection to freezing so cold that it cuts into you, maybe the suggestion is that the Red Ogre should have been willing to give up the idea of being friends with the humans, rather than lose his best friend. Perhaps it's meant to suggest self-sacrifice.