Whatever you add to a pacifist or humanist philosophy to account for cases when said philosophy would increase vulnerability of its practitioner, it is necessarily going to be in conflict with pacifism and humanism.
"When possible, turn the other cheeck; when not, be willing to blind, maim and kill."
So much for "Love your neighbor, love your enemy" and "live life appreciating our fellow man (regardless of what race/sex/country they come from). It's the human race after all."
You mean like the self-image one outwardly projects of oneself?
It is useful if it does, as this way, one doesn't run into contradictions within one's outlook (and thus doesn't have cognitive dissonances to deal with, nor has to deal with those pesky critical people who point out that one is being a false humanist/pacifist).
Depends on what is meant by "good" and "harm."