It's evil, no question about it. I said as much over in the thread about the strip and I'm not going to repeat everything I said again here.
V did it to make the dragon suffer, which itself is evil. And the whole justification of protecting V's family is ridiculously flimsy. Dragons often don't have the same bonds of kinship that humans (or elves in this case) have, so many of the dragon's family is simply not going to care that V offed her and come looking for revenge. As evil beings, they're likely to care even LESS. It's also a highly disproportionate response.
There's no way a spell of this nature could be anything less than evil.
Of all the points made in this thread, I will agree with this one:
Also, no, it's not justified. The whole idea of evil is that it's the easy path. Being the good guy isn't supposed to be sunshine, flowers, and rainbows. You see some do something unquestionably evil, yes, you stop it and then. You don't then kill it's family because they might be evil too, that makes you no different then the evil bad guy you stopped. I can't think of a single game or setting that has a meter of alignment or morality that wouldn't mark you down for it.
Yes, that's it. Two wrongs do not make a right. That's one of the whole points of good. Evil wouldn't think twice about proactive mass-murder or genocide, but good would, and might even try to stop it because that it what distinguishes it from evil. Good and evil could be defined like obscenity, you don't know how to define it, but you know it when you see it.
V did this for an evilgasm, and it's self-evident from the strip.
And the whole argument, "kill this person who's about to do a nasty evil act to protect innocents", is a lie. When we see this argument being used in fiction, who's using it? Always an evil tempter. I can't recall seeing the agents of good using this argument. The future isn't set in stone. And hey, let's bring some quantum theory into this: if alternate realities exist for every decision we ever made and will ever make, then killing someone to prevent an evil act doesn't just kill that person in the quantum realities where he does that act, it kills him in the realities where he choose NOT to make that act. It kills him in that realities where he spends an entire lifetime not doing evil or even living virtuously. Is that not evil? (And yes, if the theory is true, there are probably quantum realities out there where Hitler spent his whole life as a painter.)
Anyway, I see more or less two arguments being made for not evil here. One is V fans defending their favorite. Sorry, but V has crossed into the dark side here. Anything else is denial.
The other is the side that thinks D&D alignment is stupid as written, and the side that tends to come up with some truely ridiculous moral arguments to say alignment should be banned. Yes, there are occasional flaws to the alignment system, but as I've said before in alignment thread, often they're a result of a DM throwing a half-assed ethical dilemna on a party so the paladin becomes a fighter, or to screw some other alignment-dependant character for little more than whim. In any case, the logic behind "killing evil = good" can't possibly be sound in my mind.
And careful folks, there's a couple of places where this thread has danced around the politics and religion bans. Don't get this thread locked.