If I cast Deathwatch, an [Evil] spell to determine who is most hurt so I know who to heal first(triage) I dont consider it evil, and dont consider negative energy inherently evil either.
If I cast an army of undead, in order to hold back the tides of Demons and Devils, and save the world, I dont call this evil either. Particularly if it means saving human, elf, and Celestial lives.
I just think much of D&D alignment and morality is silly, and I dont believe in any of it. Negative plane spells used to heal are evil, Positive plane spells used to murder are good, it makes no sense and I handwave it.
Its clear the RAW is on the side of my enemy, and that casting evil spells is evil, but I dont care, and handwave it anyway.