http://www.pewresearch.org/fact-tank/2018/01/30/5-facts-abou...

Violent crime rates both in America and within the developed world at large are way down. This is usually overlooked because we've now become hypersensitized to remaining acts of violence - a "mass shooter" that kills nobody but themselves is now all over the Internet in real time, while when I was a kid in the 80s, everyday violence within large swathes of American society would just be a "just another homicide in a blighted urban area, don't go there". But by the statistics, America today is a lot safer than 30 years ago.

Now, I have no idea whether this is because of spanking or not, and drawing a causal connection is much harder in the face of all the conflating changes within society since then. But it's factually incorrect to say that "society wasn't significantly more aggressive than it is now", because it was.