I think that you need to step back, think, and rewrite/re-format your writing so that it has a degree of coherency, because to be perfectly honest there isn't much to be derived from what you've written but reactionary misanthropy which seems to stem from a sense of hurt and righteous indignation as opposed to a well-thought-out theory or thought. I'll make an attempt to answer what legible parts of your text there are.

Many human-beings have the distinct, reliable, and foolish ability to (often) completely dismiss the value of other life-forms.

How is it distinct? Does the Lion in the Serengeti have any regard for the life and wellbeing of the Gazelle? No.

On the contrary, humans are distinct among animals because we have the capacity to care for animals of other species, we have the capacity to feel something more than instinct or physical sensation, and that is why a human can feel genuine affection for a pet, or love and want to care for a child that isn't their biological offspring. No other species on our planet can feel such things, a cat may associate it's owner with feeding and safety and thus appear to care for it's owner, it may feel protective over the kittens that it's just given birth to, but it cannot feel anything beyond base-instinct. If humans weren't as we are, we would behave in a way similar to any other apex predator, we would kill for food or to protect ourselves from a perceived threat without any concept of caring about those that aren't ourselves or our young, biological offspring.

Can you tell me why it's foolish? You seem to imply that this is all self-evident, but it's not, so you're going to have to expand on why you think that is.

This is PARTICULARLY true when another life-form can be used as a catalyst for human advancement, regardless of the suffering OR even the extinction it may inflict.

You say this as a statement of fact, when it isn't. Our capacity for higher thought is why we are unlike other apex predators, and don't kill without regard. It seems that you feel indignation about the state of the environment, which isn't a problem, it's in the interest of humanity to maintain that which we've been given, but to engage in this hyperbolic misanthropy, to make the implication that members of the most advanced species that exists in the known universe are some kind of savage brutes is a statement without basis. It's laughable, in fact, when we consider that a human wrote this flagellating and incoherent diatribe.

(If you want specifics & details, just Google "humanity causing alarming extinction rates." I'm sure that will give some decent data.)

Telling me to Google it doesn't further your point. It's not my job to find information to back up your own ridiculousness. Furthermore, the fact that humans feel guilt about, and often try to prevent and/or reverse extinction, sort-of negates your point.

So, Why? Why do we behave like this? Well, for one, we tend to view our own consciousness, and the value of our life, as being GREATLY superior to EVERY other life-form on earth.

You haven't made the case that this is something exclusive to humanity, and furthermore you haven't told us why it's something wrong, you seem to think that everything you say is self-evident by virtue of it's being said.

[depressive, self-important screed that has no value or evidentiary support]

This is what I was talking about in my opening paragraph.

So, why am I writing this? Well, I'd like to get an opinion besides my own regarding this issue/discussion.

I think my opinion is clear, this is nothing more than reactionary misanthropy, spurred on by a depressed sense of indignation, which you've sloppily tried to intellectually justify with the invocation of concepts which you have very little understanding of.

For, as of late, when I do a mental-summary of ALL the pain/suffering INFLICTED by humanity, and have it compared with all the love & beautiful things SHARED by humanity, I find myself TRULY believing humanity should end.

It sounds as though you're experiencing depression, which is causing you to become incoherent.

Am I just depressed?

I don't know you, I cannot tell you whether or not you're depressed, but it seems that you are.

Or is this a legitimate view-point?

What is legitimacy? Are you conflating it with coherency or correctness? In that case, no, it is not.

From a utilitarian approach ("the greater good") wouldn't the end of humanity be a good thing? Or, at the very least a DRASTIC reduction in population?

You don't seem to know what utilitarianism is, because it's not the greater good. For something to be of utilitarian value, it must have the greatest utility. What utility is there in omnicide? Furthermore, does utilitarian value equate with correctness? In that case why should we not kill every animal that can provide us with food, cut down every forest so that we can build more homes?

What a perfect way to end this rant of yours, with a cloying plea for validation. You haven't actually said anything that makes your point.