Arguing against using public IP space

I don't want to start a flame war, but this article seems flawed to me. It seems an IP is an IP. http://www.redtigersecurity.com/security-briefings/2011/9/16/scada-vendors-u... I think I could announce private IP space, so doesn't that make this argument invalid? I've always looked at private IP space as more of a resource and management choice and not a security feature.