Short answer: Depends on GM fiat.
Paizo's Pathfinder forums already have some very long and detailed discussions of this topic, with many amusing conclusions, but no definitive rulings:
There we go, it's official. I'm in shock.
Enslaving good celestials with planar binding is now OFFICIALLY a good action because it has the "good" spell descriptor.
Or do you wish to amend that statement JJ?
It's been debated on the RPG Stack Exchange, as well.
Yes, casting a spell with the [Evil] descriptor is an evil act. Always, by definition, as black letter law in the game rules.
One [Alignment] act does not cause a character to change alignments. A pattern of [alignment] acts will change alignment. How many evil acts are required to change your alignment (or have other effects like removing paladin powers, compromising divine spellcasting, or creeping out the locals enough to get a torch-and-pitchfork mob set on you) is a judgment call for each GM. For non-religious characters, it should take a decent bit to go from good to neutral to evil. I personally would rule that if you just happened across a scroll of this thing and felt like you had to do it once to save your party's life, fine. If you put it into your spellbook and use it from time to time, that's neutral territory. If you use it routinely all the time, you switch to evil (balanced against what all else is going on with the character of course).
Now you can argue "subjective morality" and all, but in the normal D&D (and Pathfinder) cosmology, there is objective good and evil, and yes, cannibalism (especially of the "drink blood to power spells" type) is evil.
The phrase "as a matter of pragmatism" is always a warning sign for evil. People seldom consider themselves evil. Prison is full of "good people." When they rob, kill, etc. they have some "pragmatic" reason for it. His reasoning "well it's just for more power!" is a classic evil justification - heck, worst than most that are at least trying to say "it's for my family!" or some allegedly noble end.
All that having been said, it's not like having an evil alignment is the end of the world - I've GMed many parties who have included evil characters. Usually not "black robe" mmmwah-ha-haaa evil, but "well, I wouldn't normally sacrifice someone to power this spell but it's really important in this case..." I like leading characters down that path to see how bad they'll get; I bet your player would consider sacrificing sentients for spells if you lead him down that path a while. Storytelling gold! Explain to him "sure, your character doesn't think it's evil - but the gods (aka I) do. But that's not me telling you your character shouldn't do it; anti-heroes are a legit thing to roleplay."
They even have a thread specifically about the possibility of playing a Good necromancer in Pathfinder:
Of course, depending on your definition of necromancer.
Can you be creating undead as a necromancer and stay good? No, that's an evil descriptor spell.
Can you cast the dozens of other necromancy spells that aren't evil, like Disrupt Undead, Fear, False Life, Blindness/Deafness, etc.? Sure. You will probably find that you can't cast about 30% of the necromancer spell list, but you can cast spells from other schools as well. The locals may not buy your good necromancer routine, but you can sure try.
The idea isn't that preposterous; the hippie tree-hugging races even invented a way to become a Good-aligned lich - err, Baelnorn.
Also, some people made a White Necromancer prestige class, that specializes in keeping the undead in their graves.
As an interesting side note, there are some options from D&D 3.0 and 3.5 that let you tinker with the alignment descriptors on your caster's spells:
The aligned caster alternative class feature (Dragon 357, p88) adds an alignment descriptor to all your spells in exchange for your familiar. You can take it for any class that normally grants a familiar.
The 10th-level planar wizard substitution level (Planar Handbook, p36) adds an alignment descriptor to all your spells in exchange for the normal bonus feat.
Intriguingly, the alignment descriptors 'stack', in a way, since a planar wizard who has chosen to add the Evil descriptor to all her spells gains a +1 CL bonus against Good creatures; if she casts a spell that would normally have the Evil descriptor, she gets a double whammy, i.e. a +2 CL bonus against Lantern Archons etc.
Planar Spellcasting (Su): A 10th-level planar wizard learns to channel planar energy through her spells. Upon gaining this ability, the wizard chooses to make her spells anarchic (chaotic), axiomatic (lawful), celestial (good), or fiendish (evil). Her spells gain the indicated alignment descriptor. The wizard can choose any of the four options, regardless of her own alignment. Against creatures of the opposed alignment, she gains a +1 bonus on caster level checks made to overcome spell resistance, and her spell save DCs are increased by 1. If she casts a spell that normally has the same alignment descriptor that she would apply, or whenever she casts a spell on a plane with an alignment trait that matches the alignment she chose, the bonuses increase to +2. These effects apply only to the character’s wizard spells; any spellcasting ability gained from another class functions normally. For example, the spells of a wizard choosing to cast fiendish spells gain the evil descriptor. She gains a +1 bonus on caster level checks to overcome the spell resistance of good-aligned creatures, and good-aligned creatures attempting to save against her spells do so against a DC that is 1 higher than normal. If she casts a spell that would normally be an evil spell (such as contagion), or if she casts any spell on an evil-aligned plane (such as the Abyss or the Nine Hells), these values would increase by 2 instead of by 1. This benefit replaces the bonus feat gained by a standard wizard at 10th level, as well as the two spells a standard 10th-level wizard learns for free.
It doesn't mention any effects if, say, a caster adds an Evil descriptor to a Good spell, or vice versa.
Again, depending on a GM ruling, this could be interpreted as meaning that it's possible for a spell to be both Good and Bad. At the same time.
Schrödinger would be so pleased.
Unfortunately, that ruling might be opposed by the description of the Aligned Spellcaster:
Your passions drive your magical abilities, imbuing your every spell with the power of your conviction. Those who oppose your ideals suffer the most from magical energy.
Level: 1st (4th for hexblades).
Replaces: If you select this class feature you do not gain a familiar.
Benefit: Choose an alignment component you have that is not neutral. Spells you cast gain the appropriate alignment descriptor unless they already have the opposite alignment descriptor. For example, a neutral good wizard who selects this ability (and who must choose good) casts all spells that aren't evil spells as good spells.
PS: Who is this 'Nick' person of whom you speak? He appeared in the background of several of the Shattered Star episodes, as well.