This is really a very interesting discussion.
Let me throw in a few more bits of information. The cleric started out as a rogue (more of an acrobat than a thief, but definately chaotic). He was impressed by the monk in the party, who was a follower of a nature deity. The player told me that he wanted to switch to cleric, so I arranged for the character to have a "vision" of this nature deity when it was time for level up. He then took his next level as cleric, and plans to stick to being a cleric from here on out. The player is really trying to role play this character consistently. He thinks that a newly converted cleric might be more extreme in his views than one who had been practicing the faith all his life. Since the deity is a nature god, he is comfortable with the idea of natural life being violent and bloody. The strong survive, the weak do not. Anyway, the cleric is struggling to be what he thinks he should, and it has been very interesting to watch this player roleplay this struggle.
The adult kobalds that the players killed in the mine were a remnant of a larger band that had been attacking the village, and had killed dozens of townsfolk already. If the players had brought kobald infants into town, the residents would have killed these infants, and probably considered the PCs to be traitors, or at best insane. The entire party knew that they could not bring the kobald infants back to town, because the cleric suggested it, then admited it was out of the question.
I think that the action was not evil, but I agree with those of you who have suggested that it could be a step down that road. We'll just have to wait and see.
