How bad?
Let's see. The Sahara Desert used to be a wooded savannah. The Ice Age killed most of life on earth. The Medieval Warm Period got pretty warm, it enabled exploration to expand. Agriculture started on previously ice bound areas.
None of that had anything to do with polluting the atmosphere and activities of mankind. So, whatever the climate does, it has nothing to do with us.
No, the ice age did not kill most of the life on earth. In fact, the last period of extinction, not counting the ongoing extinction event, took place when there was a very rapid climate change, the Younger Dryas, warm to cold, 12.9 thousand years ago, and cold to warm, 11.6 thousand years ago.
What Caused the Younger Dryas Cold Event?
This was especially true on the North American continent. We lost all of the mammoths and mastodons, in North America, horses, camels, and a couple of specie of bison.
As for your other rather idiotic arguement, since nobody was killed by a gun prior to 500 AD, guns cannot kill you.
Guns are not a natural, repeated, cyclical occurrence. Warming and cooling IS.