I'm in the middle of revising my thesis, and at the moment I'm in the middle of an attack on an entire planet. A planet of creatures that have no desire other than to kill and enslave and create more of themselves (as most bad creatures tend to do). This is not Ender's Game. The bad guys here are not bad through a misunderstanding. There is no failed communication. If you fight them, they will kill you. If you are a woman, they will cut out all your reproductive organs and then let you heal enough to put you in a slave camp. If you are weak, you will die. If you are strong, you will be implanted with an explosive device. If you try to leave, you will die. If you survive all that, you will be a slave until you die. There is no handful of nice creatures in this species. They engineer themselves this way on purpose because they like the violence, the power, and the destruction.
I've put this in pretty much everywhere in my book to illustrate that these things are bad. No redeeming qualities. They're smart, but they're not going to share. Everything else is inferior to them and should die or serve (and eventually die).
Now, in the finale of the whole thing, the game plan (and not created by humans or Earth) is to wipe them out. A fleet moves toward the enemy homeworld in order to do the job and in doing so, lure the enemy ships back from what they are doing at present - attacking Earth (and we are not the first, and would not be the last). And as the bombardment begins, the main character thinks, Surprise, surprise, you sons of bitches, and there is a note from one of my critique members that says, "He's really eager to destroy an entire species. That makes me sad."
Now I love the girl, but that mindset makes me want to tear my hair out. Why? Why is this sad? That he's pissed off and wants them to stop killing people on his planet? That he's not sorry they're all about to get what they've been dishing out to a number of planets over the years? Sad that this fleet is about to kill off a genetically modified species that is not in its original form, will never be again, and would be equivelant to allowing a pack of rabid dogs run around your house unchecked?
We killed off an entire species in Independence Day. Did anyone think that was sad? Luke Skywalker blew up a Death Star which also happened to be full of people. Who thought that was sad?
People on this planet will freak out when a bear or tiger or other animal kills a person and demand that the animal be "put down" (just a nicer way of saying "Kill the bear before it kills someone else.").
I guess I just don't understand the mindset. Maybe I'm just different. I don't feel empathy when a suicide bomber is killed before he can blow himself up at a market and kill 50 people. I simply do not feel sorry for people who wish to deal death and destruction upon others who are merely going about their day.