Below is the Bestiary 6 description of the Animus Shade's Mental Schism ability. Looking for confirmation that this ability results in this particular evil undead being unaffected by a Paladin or celestial's Smite Evil because Smite Evil is alignment based.
Mental Schism (Su): An animus shade’s
mind is a chaotic tangle of shredded
remnants of the dominant personality
that once subsumed it. This mercurial
state of being is too piecemeal for
alignment-based effects to take hold.
The animus shade is immune to all
effects that are dependent on alignment.
Seems clear to me that it's immune.
Yup. I imagine Smite (and probably Protection-From-X spells) is the main reason they put in that bit about being immune.