You are absolutely correct about the long history of dramatic climate change on planet Earth. And, life and Earth are absolutely not in peril. I am dead certain that, as has happened uncountable times over the last 3.5 billion years of life on Earth, climate will change, and the flora and fauna best suited to the new climate will thrive, while those that cannot adapt fast enough will not. So what is in peril is not life. It is human civilization. If we can slow the rate of climate change so that people can adapt, humans may survive. If not, they may disappear. Adaptation typically takes many, many generations. Dramatic climate change over a short period of time usually results in the extinction of the dominant genera.
One could argue that humans are in even greater danger from loss of potable water, ubiquity of potentially harmful chemicals, population crash due to disease or mass starvation from overpopulation, but that does not lessen the threat from too-rapid global climate change. If it is not human-driven, then we are all simply screwed anyhow, so we can whistle away on our summer days enjoying what we have left. But, if there is a chance that we can slow it enough to adapt, wouldn't that be smart? I have been one of the ones pointing out that CO2 is not the whole story. Methane and water vapor are more eficient greenhouse gasses. But we have leverage on CO2. Think of CO2 as a hand on the valve of climate change. If we can reduce CO2, which may reduce production of other gasses through limiting the positive feedback mechanisms (see my posts above), isn't opposing mitigation just sticking our heads in the sand and *hoping* for a good outcome?
And now for a sudden turn - perhaps the extinction of humans *is* a good outcome for planet Earth. Or (more likely) perhaps it just doesn't matter to planet Earth in the long run since the supernova of Sol will take it out eventually.