Let's take the initial argument piece by piece. NOTE: I don't actually believe or live by all the things I'm about to say, but I've been told to come up with a rebuttal to information given me, and so I will. That's debate for ya'.
Humanity has spread across the surface of the planet like a cancer. Destroying ecosystems and species at a rate of 580 extinct species per day...
I am willing to believe that 580 species per day go extinct, and that many of those extinctions are due to human behaviour, but hundreds of species were dying out daily before humans ever came into the picture. It's something called Natural Selection. And there's a reason "Natural" is in there. Even the species that do go extinct due to our behaviour isn't necissarily a sign that we shouldn't exist. The activities of different varieties of animals have caused the extinction of other varieties for millions of years before our arrival as well, and if you look as humans as another sort of animal, than can't we as well?
And if you don't look as humans as animals, but instead as some sort of greater being, such as children of God, then isn't our existence more important?
And we have noticed this behaviour and are taking progressive action to fix it, saving many species and bringing them back to full health.
Whether you look at it as God or Evolution, the dying out of other species is simply a sign of Survival of the Fittest, and we win. Since when is winning something to be ashamed of?
...allowing hundreds of thousands of our own kind to die preventable deaths per day, ...
Many of these preventable deaths come through choices individuals make, such as cancer from alchohol, tobacco, or other kinds of drugs, or eating improperly and thus becoming obese, which brings on other diseases, or HIV, which is most commonly spread through unprotected sex. In order to prevent these from spreading you would have to impose upon the angency of others and their right to make their own choices. Trying to stop these would impose on people's rights to choose to govern their own eating habits and love lives, which should really be their own affair. And I think freedom is a more important cause, on the whole.
The other deaths from preventable disease, such as the epidemic of tuberculosis in Russian prisons, are getting addressed, and taken care of. These are primarily the fault of a select few individuals, and are not a justifiable representation of the population as a whole.
Otherwise disease comes from ignorance, and not knowing any better has never been a good reason for xenocide in my book.
...eliminating vital and amazing genetic diversity...
Actually, in the more modern era, where long distance travel and communication is a daily activity, interracial and intercultural marriages are more and more approved of, sex is more free and common, and the incestual tendencies of many European royals are starting to dissolve, genetic deversity is thriving. I have no idea what this idea is based off of, but it is incredibly false.
...pillaging the planet for resources, then dumping the poisons extracted from these resources into our common atmosphere, and generally f**king everything up for everyone who doesn't happen to be Human...
Guilty as charged, but the incredible thing is how many programs and how much awareness and work to fix this problem exist. Any species that as a whole group can say "We're idiots" and then
reverse their own damage deserves to exist, if only for that ability. Gazelles and other animals have been known to go outside of their normal grazing grounds due to natural disasters and completely destroy previously existing ecosystems and then humans step in to fix it. We are the only creature capable of fixing ours and other animals destruction conciously and on a massive scale. And so yeah, we f**ked up, but
we're fixing it, and that justifies everything.
For, after all our cancerous behaviour to our homeworld, we behave the same to one another as well. .... Even in well-fed developed nations, Humans still beat one another, rape one another, kill, steal, and act like total bastards with alarming regularity. Often, there isn't even any reason whatsoever for any of it. It doesn't take much to turn gentleman into raving savage, that seems clear enough.
Sadly, these actions are common to almost all mammals, and if it's not a reason to kick wolves out of the system, it shouldn't be for humans either.
And we punish those who commit these acts, which isn't true for most animals. We recognise them as wrong and theives, rapists, and murderers wind up in prison when possible. Is the system perfect? Hardly. (See "Tuberculosis in Russian Prisons" above). But we do make an effort. In the wild, dominating, wounding, and forcing sexual actions on others in a pack can give an animal power and prestige. In the human world, it takes them away. This is much more appropiate.
A lot of the next stuff seems redundant. We are power-hungry and we don't care who step on to get it. Okay.
We think in the short term, and act even shorter, perpetuating brutal injustices while we claim to value our unbiased judiciaries. We're all doing it right this minute, continuing to stomp third-world nations further into the mud via our preadatory, capitalistic lifestyle. Heck, we've organized entire international agencies to more efficently exploit and ruin 80% of Humanity for the benefit of the other 20%
If you completely kill the capitalistic lifestyle (though there are many things I think America could drop the capitalism on, but whatever) then you end up killing diversity and free will as well.
Oh, and ambition.
Yes, capitalism sucks. I agree. People up top really should be lending a hand to those down below. But if you force them to on too large of a scale, then that infringes on the rights of the people in more fortunate standings.
And the "stomping" on various third world countries is often the first step to their becoming second world, and then first world countries. Giving them jobs and making them work for larger corproations gives them to opportunity to work on a larger scale, and communicate outside of their country, and then question their own lifestyle. Education doesn't exist in many places until they are given a situation in which they question the poor ways in which they are being treated, and then seek for higher things.
Wouldn't a better option be to just offer education and good jobs in those places?
Yes. I'm not going to lie. You have me beat there.
But this is another case of a small amount of people doing a lot of bad. If it really is only 20% taking advantage of the othe 80%, then you are suggesting that 80% of the population shouldn't be allowed to exist because of the actions of 20%, and that isn't reasonable. 20% is a minority in a much larger group.
How can we justify our selfish, self-centered, murderous, destructive, shortsighted, and savage behaviour? What right do we have to destroy everything we touch with frightening amorality at the expense of every other living thing?
Well...much of our destructive behaviour are similiar to that of animals, and so we justify it the same way animals do. If animals don't have to justify their behaviour, why should we?
And if we are higher than animals due to divine right, then if at any point we should not be allowed to exist, God will see that we don't. (Floods and plagues, anyone?) If we still do exist, then we are justified simply because God is allowing it, and God is all powerful.
"Expense of EVERY other living thing" seems a tad extreme to me, but that aside...
We destroy in order to create. For our own benefit? Yes, most of the time. But isn't that creation, that ability to create incredible and almost unnatural things that no other animal could manage a justification of our existence? Think of your favourite paintings, movies, songs, and foods. Many of those materials came from very unnatural means, especially if your favourite songs include instruments made of plastics or synthetic materials, and if you listened to them on CD.
Whether through Evolution or God we can create from what we experience. We can reflect on what we see, and write and take record.
The greater the bad, the more aware of the good you can be. You don't appreciate the comfort of your own bed until you are away from home. You never know how good anything is unless there is something bad to compare it to. Opposition is essential to happiness.
The species we are killing off are not aware that they are being destroyed. It doesn't effect their happiness one smidgeon if their death is impending due to us. Their happiness is based entirely on instinct, and the have nothing to compare it to, and thus no real diversity , and what is the point of that?
Humans should be allowed to exist because we can know and understand the animals in ways they can't, and we can experience and understand their lives, and so we are the creatures in this world really capable of happiness and sorrow. What is the point of a world without those?