The Galactic Government does not protect humans from the consequences of their actions unless it is to prevent the destruction of earth

 So, things like Global Climate changes brought on by slash and burn techniques for farming and burning down whole forests during wars and burning fossil fuels like Gasoline and diesel and these kinds of things we are not protected from. But, earth is protected (generally speaking) from other civilizations making war upon us. So, mostly they observe us like we would wild animals in national parks on earth. We are a part of the wild life on earth.

However, when we mess up the planet ecologically and create what is happening now it is considered a natural thinning out process that we are creating ourselves and so it is unlikely that we will go extinct but rather be "majorly thinned out" this century instead by the consequences of human actions of at least the last 25,000 years of what humans have done here on earth.

So, it is not so much that humans are creating an extinction level suicide of extinction and much more likely that 9 out of 10 humans (number wise) will gone from earth by 2100 AD.