It has been established that using spells with the [evil] descriptor are evil acts (duh), and raising/using undead is evil (understandable). My question is, does using negative energy in any form constitute an evil act?
Examples:
Rebuking/commanding undead?
Powering a divine feat like DMM?
The Player's Handbook says, "Even if a cleric is neutral, channeling positive energy is a good act and channeling negative energy is evil" (160).
The Divine Metamagic feat, in part, says, "As a free action, you can take the energy from turning or rebuking undead and use it to apply a metamagic feat to divine spells that you know" (Complete Divine 80). The phrase take the energy sounds, to this reader, like shorthand for take the positive or negative energy, that, in turn, sounds suspiciously close to normal channeling of negative or positive energy—making the act of taking the energy—possibly—evil or good, depending on the flavor of energy. However, a DM can totally rule otherwise, and another reader may read this in a wholly different way.
Note that documented, actually-called-out-as-evil evil acts are incredibly rare in the core rules—so far as I'm aware it's just this evil act and "trying to dupe someone into buying a cursed item" (Dungeons Master's Guide 277). Further, given the seemingly capricious way in which spells seem to have been given the descriptor evil—the inoffensive 1st-level Clr spell deathwatch [necro] (PH 217) possesses the descriptor evil, for instance—in some campaigns not even casting a spell that possesses the descriptor evil will be an evil act.
In other words, while the rules say that channeling negative energy is an evil act and, therefore,—maybe, by extension—taking the energy from rebuke attempts to power divine feats is also an evil act, expect table variation, especially if—like in many campaigns—the role of alignment is vastly reduced or even eliminated completely.
Channelling negative energy is an evil act (Player's Handbook p.160), as is the negative-energy using spell curse water (p.216).
However, not all uses of negative energy are stated to be evil.
The spells touch of fatigue, enervation, ghoul touch and inflict light wounds are described as using negative energy, but do not have the [evil] descriptor, meaning they are not inherently evil.
The negative energy plane (DMG p.157) is described as antithetical to life, but it is not evil-aligned.
The spell negative energy aura (Planar Handbook p.101) is not an [evil] spell. Entropic creatures (Planar Handbook p.123), which use negative energy, are not specifically evil.
