[qiqing]

Also from the article, modern medicine:

"We have firearms, but we also have emergency services," he said. "It's easier to kill, but easier to save lives."

[iguy]

This is true, and both make a difference.

But worth knowing that the murder rate dropped, over centuries, to be extremely low around 1900 say. At this point medicine wasn't very useful at saving lives, and while guns (even machine-guns) existed, they weren't in the hands of every street-corner criminal.

So there was enormous real progress over the time-span separating us from the medievals. Trying to figure out the impact of modern medicine etc. is more relevant for trying to understand e.g. the rise & fall of crime since 1960.