Okay, found it:
Code:
modifier = {
factor = 1.5
OR = {
has_citizenship_rights = yes
can_be_military_leader = yes
}
from = {
owner = {
any_neighbor_country = {}
NOT = {
any_neighbor_country = {
OR = {
is_hostile_to = from.owner
is_domineering_to = from.owner
is_rival = from.owner
}
}
}
}
}
}
So Pacifist attraction is increased for any pop with Full Citizenship or Full Military Service, so long as (1) there is at least one neighboring empire, and among the neighboring empires, (2) none have the "Hostile" or "Domineering" attitudes toward the pop's empire, and (3) none are rivals to the pop's empire.
I tested this by rivaling my newly discovered neighbor, causing it to change to the "Hostile" attitude. My empire's Pacifist attraction immediately went away.