A drill that will consume the heavens

At this point I'd hesitate to consider Tengen Toppa Gurren-Lagann's Anti-Spiral faction as being explicitly anti-life. Maybe they're silicon-based life. It would go some way towards explaining Nia's SHODAN makeover. Even if they were, we're almost obligated to support Spirals, DNA, and other symbols associated with carbon-based lifeforms. Not only are they ridiculously cool, we also happen to not be droids.

Although if you are, that's cool too.

One can't completely write off the Anti-Spirals as generic bad guys, as SHODAN Nia offers an interesting, if brief, commentary on carbon-based life. It was probably brief because it's depressing to contemplate the big picture. Spirals are viewed as this grave threat to the universe because life does what life does: consumes and multiplies without consideration. It thus fell to the Anti-Spirals to put carbon-based life in its place, which is to say, in convenient and easy to manage boxes, with the threat of complete extermination to keep them from expanding outside of their boundaries. Eventually, in theory, the molten crust of the respective planets would cool, and they'd all die anyway, causing minimal additional damage to the cold and austere beauty of the universe.

It's a situation that plays out all the time, with humans in the role of Anti-Spirals, and weeds, pests, and even other humans in the role of Spirals. Trying to stem the vicious rampancy of growth and consumption sounds like a just and responsible thing to do, especially when described with terms like vicious and rampant, until the realization hits that doing so may involve some messy details, like inducing resource starvation or just plain death.

Beyond that, Spirals are also agents of chaos. It's evident, even now. We like to burn our dinosaurs fossils, kill animals, kill trees, kill each other, dig stuff out of the ground, and generally engage in the very clean practice known as industry. What would happen should humanity ever escape its current confines and run amok throughout the universe? We'd be like this unstoppable force of entropy, vacuuming resources from planets and asteroids, gobbling energy by creating our own stars or just subjugating existing ones, and generally accelerating the level of decay all around us.

Spiral power is the desire to survive, whether that involves fighting, consuming resources, or multiplying. It exists even while doing so means that the necessities to that existence are slowly eroded. To an entity like the Anti-Spirals, Spirals are just out to consume the entire universe, and then die out when the job is done.