Job Alignment Chart

[Alexz]

A Black Mage tapping into the powers of the Void doesn't inherently make them evil. There's power, and there's how you apply that power. An individual Black Mage could be considered evil if he burned an orphanage, but that hardly reflects on all of them.

Main reasoning for evil:
“In days long past, there existed an evil clan and arcane art known as black magic—a potent magic of pure destructive force born forth by a sorceress of unparalleled power. Those who learned to wield this instrument of ruin came to be called black mages, out of both fear and respect for their gift. Yet great power served to corrupt the judgment of mortal man, and so he unknowingly set out upon the path of ruin.
Adventurers who take the black will become agents of devastation, capable of annihilating those who oppose them through little more than the force of their will.”
—Game Description

[Ashkendor]

Main reasoning for evil:
“In days long past, there existed an evil clan and arcane art known as black magic—a potent magic of pure destructive force born forth by a sorceress of unparalleled power. Those who learned to wield this instrument of ruin came to be called black mages, out of both fear and respect for their gift. Yet great power served to corrupt the judgment of mortal man, and so he unknowingly set out upon the path of ruin.
Adventurers who take the black will become agents of devastation, capable of annihilating those who oppose them through little more than the force of their will.”
—Game Description

The War of the Magi is hundreds of years in the past. Modern adventurers have nothing to do with that "evil clan" from ancient times.

I mean, on one hand you say SMN are "summoning demons" but since they do it for the good of the party it makes them Neutral instead of Evil. Black Mages are channeling the power of the void for the good of the party. Why is that any different?

Play the DRK quests if you havent already... all I will say

I have. Lawful Evil is completely wrong for DRK. They protect the weak and innocent.

[Alexz]

I mean, on one hand you say SMN are "summoning demons" but since they do it for the good of the party it makes them Neutral instead of Evil. Black Mages are channeling the power of the void for the good of the party. Why is that any different?

Well, the reason why they would be neutral as opposed to evil would be because they respect the lives of the primals. Rather than harnessing dark powers, they are purifying controversial bad powers into controlled good. However, they are still neutral as opposed to good because they use that power to get rid of enemies. By killing other beasts, it could be hypocritical, as they are purifying and taming one while killing the other.

BLM, on the other hand, do not purify the black magic. They control the devastations and use it for more destruction, which isn't necessarily bad, but evil in terms of the WoL alignment spectrum of what evil can be.