He says something to this regard in the following video:
http://archive.org/details/StevenPinker_2007
See 11:00ff forward. He also says that anarchy is an excentive for violence.
I haven't fact checked everything, but I am actually pretty skeptical about this. He also gives other reasons.
Read his book on the subject 'The Better Angels of our Nature". It is a pretty long (800+ pages), but informative book.
I think it can more easily be said that certain things in modern state compared to older states. But which arise not from the state themselves, but certain civilizing impulses away from violence. But these are partially embodied in the state.
My interpretation is that two things have happened: state power is more subtle. But people's preferences for violence have declined. But people cannot see that the state is violence, because of the subtle propaganda that makes it seem not so. For instance, it can use media and schools instead of guns to force obedience. And a few people who use violence can be sorted out.
You mean there is actually other reasons that lead to less violence and that those reasons just coincide with the emergence of the state as institution? I with thinking this, too. Coincidence doesn't make for causality.
Yes, the nature of violence may have changed. More symbolic violence then visible physical violence. Also sugar-coating the violence in procedures cloaking it to appear as "authority". Take for instance a instructional letter to you, i.e. telling you to pay (your?) taxes, if you refuse, you get a court order, if you ignore that, there will be a warrant and if you resist the arrest, they finally will use violence against you. Still very subtle and also using overkill in terms of man-power. It is of course still violence, but accepted, because people believe into the legitimacy of the state and perhaps in his monopoly of violence.
OK, I think we discussed social contract theory elsewhere.