This conversation is specifically about purging so of course there's no talk about the balance of pacifists, just like there hasn't been any discussion on any of the other ethics either.
The fallacy of your argument is that by us saying that the xenophobic game needs rebalancing DOES NOT mean that the pacifist game doesn't (I personally wouldn't know as i can imagine it being boring as fook).
For the pacifist strategy to be equally as broken it would need all of your citizens to down tools when you're at war (as obviously pacifists wouldn't support military action) and all your military ships surrender instantly and then we can just say that to play pacifist you're meant to avoid wars entirely...
Perfect example of Pacifist "Empire" is Galactic Federation from Star Trek - they avoid war as long as possible, and at war they try to keep as much humanity as they can - but they do not avoid wars for all cost. War is the last option, but is still fully respected.
IMO it should not be named militaristic vs pacifist, but militaristic vs diplomatic. It is much more precise, since fanatic pacifist are either forced to change their ethos ASAP, or are doomed to die in first conflict/