It's relative. It's also a balance. Anything can be a plague (including humans) if you have too much of it. Plenty of other species have ballooned in size over time, but there's a system of checks and balances in nature that bring them back to a manageable level (predators, food sources, natural disasters, etc). Humans are exempt (now) from most of these checks and balances because of our ability to significantly alter the environment around us with technology to suit our needs. So, if we wanted (and we appear to want to) we can theoretically go on expanding our population as long as we have the ability to feed ourselves. We may be able to stave off things like disease and famine for a certain period of time with our technological prowess. However, we haven't figured out a way to stave off war (the third population control of humans throughout our history) and if we don't end up nuking ourselves, then our increase in population will necessarily have to come at the expense of other species. We're in a closed system on Earth, so if one element in that systems grows, the other elements must shrink. So to an animal or plant that we drive to extinction, we could certainly be viewed as plague. However, plants and animals don't write the history books, and since we're the only sentient beings on the planet, our opinion is the only one that matters to us. So whether or not you see humanity as a plague is dependent upon the importance which you place upon human life. If we're the top dog (no pun intended), then we come first, at the expense of everything else. Wall-E took that too the extreme, simply portraying a world in which humanity had crowded out literally everything else and as a result (and a result of our own lack of sufficient ingenuity it appears) was wiped out. At the end of the day, however, it was a cute movie about some robots and if you think it's REALLY part of the liberal agenda to corrupt and brainwash America's youth, I'd just say you were being alarmist and that you should chill out. If anything, appreciate the technology that went into making the movie. Pretty impressive for its time.