According to the top rated answer to this question the only thing that makes something "of the Dark Side" is "if you are using the Force out of anger, lust, greed, vengeance, or fear, you likely channel the dark side".
In some books Jedi think that other Jedi are doing things "of the Dark Side", when they are not displaying these emotions; they are only acting aggressively.
Some relevant quotes:
Anakin obeyed quickly, Welk less so, and Anakin watched in silence as the Dark Jedi used the Force to strangle the life out of the creature........"You used the dark side!" he [Zekk] hissed.
From Star By Star by Troy Denning
In this situation it did not seem that Welk was acting with Dark emotions, only reacting to the threat to Anakin's life, but yet Zekk accuses him of using the Dark Side.
The corvette lashed out with plasma cannons and magma missiles, and Anakin's display filled with streaks of red energy. Nothing wrong with Big Eye's sensor package. Kyp had destroyed the shuttle....how? The Force? It didn't seem possible. Only the most powerful Jedi could use it that way; only Dark Jedi would.
From Star by Star by Troy Denning
In this scene (although it turned out that Kyp did not use the force to destroy the corvette) Anakin does not even ask himself what Kyp's emotional state is....he just implies that any such use of power (regardless of why you are doing it) is of the Dark Side.
So my question is can you use the Dark Side without the negative emotions normally associated with it, or are Anakin and Zekk just being overly judgemental in the quotes?