He knew Genis didn't mean to imply that they could sacrifice Martel--he knew how much she meant--so Mithos forgave it.

But Genis was still naive, still too optimistic...

He couldn't say he disliked those traits. However, Mithos knew it would only hurt them in the end to allow him to hope for a possibility that didn't--couldn't-- exist.

"You really care about them," he observed softly, almost melancholy as he rested his free hand at his side again. His voice hardened as he continued, though--to drive home the truth that Genis had to acknowledge. "But you need to stop, Genis. You chose what was important to you; now you need to sacrifice what's necessary."

He placed his hand on Genis' shoulder, gentler again. "I'm only telling you this for your own good. It's just not possible to save everyone."

So they had to choose what was most important to them, and it certainly wasn't the world that wouldn't help them.