Working together in a time of need was the best bet. Levi nodded in agreement, and did note also that it didn't seem to happen on a large scale here. Then again, there were quite a few people. Herding cats would likely be easier.
"I suppose it is subjective. I'm not sure pure altruism exists at all. And you're right. Erwin is a good person, in his own right. Not perfect, but it wouldn't stop me following him or his command wherever necessary. But what made you decide he was more worth it than someone else might be?"