I am more the first type...my take is that, even pacifist clerics understand that there are SOME situations that can only end in violence...if a Balor is rampaging at the party, and the pacifist's powers cannot simply calm/stop/disable/banish it, then the only answer is to fight...I think as long as the pacifist doesn't become directly involved, in the slaying, it's ok. After all, the Vows are about not personally engaging in an activity, not never witnessing such activity. They would probably feel sad and maybe guilty that they had to witness something die, but in the end characters are wise enough I think to understand that they can't pacify the entire universe....
However I tend to NOT extend the Vows to things like Balors, which are physical manifestations of evil and slaughter and cannot be anything else...even an Apostle of Peace, I think, would understand that these things are beyond peaceful solutions, at least, because of their very nature. (Hence the Apostle of Peace's Censure Fiends ability...) They wouldn't be like "YES! SLAUGHTER THE EVIL!" and actively try to kill it, but maybe be more like, "Hmmm, such a pity you can't see the light of goodness...I cannot help you nor protect you from my comrades' wrath..." and help their comrades how they can but kind of avert their eyes to the horror or killing. Or something.