Think about it. The carbon didn't spawn in the earth, it got deposited there. Coal and oil are sediment based. It used to be in circulation previously. And yet Earth is still habitable.
It does not. It means the mean will be at +2C. At this level of warming, we'd see crazy +15C / -15C swings regularly in many areas, often in a matter of days. It means plants that have started growing in earnest suddenly are in the midst of serious frost, killing them (something we're already seeing in my country in the EU, regularly). It means potentially many climate tripwires being triggered, too.
+2C is hell for tens, possibly hundreds of millions of people. And we're likely not stopping there.
I challenge you to back up the +15C / -15C numbers.
For humans? We did not exist for most of that chart. There's only one peak that coincides with the 200000 or so years of human existence, and your chart shows us on track to beat it. We don't have records from 100000 years ago either, we know humans as a whole survived and that's about it. I think it's a bit presumptuous to extend that to all 8 billion people alive today.
I guess my point is that it's possible that humans will survive this AND it will be catastrophic for our society.