General Kaliero
F = ma, beeyotches.
Ever since RotS I've regarded the Jedi belief system as flawed. It leaves open gaps in important situations and is often self-contradictory.
A Jedi is supposed to be emotionless. If that's the ideal for a Jedi, they lose the essence of what makes a sentient being. If the ideal Jedi is emotionless, 'droids would be the height of Jedi discipline.
The truth is, one cannot uphold a moral code without some sort of emotion. Emotion is what decides morality: you are pleased when you perform an act you deem "moral" and displeased or guilty when you perform an act you deem "immoral."
Even overlooking the flaws in the Code, the Jedi themselves do not strive to be emotionless. What about Obi-wan's call of "I loved you!" to Anakin? Even Yoda, the greatest of the Jedi Order, shows sadness and disappointment, such as Luke's failure in the tree on Dagobah.
As for the morality of certain Force abilities, that's just a product of flawed Jedi thinking. The Force is a tool. Its actual uses are determined by what it is; its practical uses are determined by the user.
No matter the user, the Force retains its double-form of Yin and Yang. Just as Yin complements Yang, the Light Side complements the Dark Side. Neither can exist without the other. There is not an absolute system of Good and Evil; the only true difference is in the span of abilities/attributes associated with each one.
So Force powers like Grip and Lightning are pushed into the Dark Side, because they use emotion. Apparently, Healing requires no empathy for the "patient" and is therefore a Light Side power.
But how do we know those who use the Dark Side aren't able to tap into the Light Side? In fact, have there been any purely Light powers in the movies, things we've seen the Jedi do that the Sith cannot? I sure can't remember any.
Therefore, like Palpitine said, the Dark Side is simply the other half of the Force, and a true master must know both sides. The Jedi are restricting themselves.
So in answer to the original question, yes, a "good" Jedi COULD use Lightning, but they aren't going to because of their beliefs.