The amount of life and species lost to human activities already makes the past few thousand years a major extinction event in line with the 5 other major ones. With this fact in mind taking the stance that this is OK because "life had to face a rapid and drastic climate change" is the moral equivalent of saying killing most of the life is OK because it happened before. That is morally repugnant. I do not think are morally repugnant so I must presume you are unaware of the facts I just presented.
CO2 stays in the atmosphere a long time. If we keep putting there permanently. If we kill ourselves (not with CO2 but with wars caused by the resource availability changes caused by climate change) then what happens during our "rounding error" many will still be dead.
The planet will probably be fine, the Bay of Texas will probably be fine and my newly made beachfront property in Omaha will be damn fine. If you live on a coast, get most of your goods by boat or live in one of the areas that will tear itself apart in useless resource wars then the eventual cooling trend doesn't help you and has no place in this discussion.