>At present, the rate of extinction of species is estimated at 100 to 1,000 times higher than the "base" or historically typical rate of extinction (in terms of the natural evolution of the planet) and also the current rate of extinction is, therefore, 10 to 100 times higher than any of the previous mass extinctions in the history of Earth.
From wikipedia, Holocene extinction. By what other metric could you possibly define "killing the planet" than killing the life on it?
I hate this argument because it feels like moving goalposts. For one thing, I don't think its hyperbolic to say that an uninhabitable planet is dead. It's dead as far as it matters to us. Moreover its so hard to read something like that and not feel like the message is "Don't worry, it'll be okay". If life is reduced back to single cells, is that okay? Will the planet still not be dead? If there is still water and organic molecules, so that life may evolve in the coming millions of years, is the planet still alive?
Due directly to human actions, species are dying faster than they ever have. Global warming has the potential to erase more species than ever before. Given the speed it's happening at, it may be a very real possibility that plants will not be able to adapt to changing conditions. Given that, it may be a very real possibility that the overwhelming death will cause runaway greenhouses faster than new plant and ocean life can reverse it, which would end all life on earth.
Life on earth would probably survive a nuclear holocaust. If you wanted to have the beast chance of permanently killing all life on this planet, this isn't far off from how you would do it. Push as much co2 as possible into the air as quickly as possible to change global conditions enough to kill all plants at the same time. If you just try to nuke everything, you'll leave a niche that other organisms will expand into. It's like antibiotics- you can't take just one huge pill, you need to keep taking them to make sure absolutely nothing survives.
Saying we aren't killing the earth is like watching someone that is getting stabbed repeatedly and saying he still has blood left.