Excellent points by Zooko.

I think it is illuminating to compare the internet to another
innovation in communication: there was an increase in armed
conflict in Europe lasting for centuries after Gutenberg's
invention of the printing press.

The printing press encouraged the dissemination of new ideas on
morality: new "ethical arguments".  Of course most of the ethical
arguments were Christian in nature.

I don't remember the author of the following hypothesis, but I
think he is a professional historian: disagreements over these
new ethical arguments caused an increase war and violence.

Some significant dates:

1450.     Gutenberg invents the printing press.
1517.     Martin Luther posts his 95 Theses.
1568      Start of the Eighty Year War between
          Catholic Spain and the Protestant low countries.
1597.     Francis Bacon publishes 3 books.
1618.     Start of the Thirty Year War.
1632.     Galileo publishes _Dialogs_.
1637.     Descartes published _Discourse_.

>From La Wik's article on the Eighty Year War:

>The Dutch Protestants compared their humble values favorably
>against the luxurious habits of the ecclesiastical nobility. The
>Protestant movement emphasized Christian virtues of modesty,
>cleanliness, frugality, and hard work. Symbolic stories from the
>New Testament, featuring fishermen, shipbuilders, and other
>simple occupations, resonated among the Dutch. The moral elements
>of the rebellion represented a challenge to the Spanish Empire.

Since the internet is now 37 years old, it might prove worthwhile
to try to identify an ethical argument that was disseminated
through the internet, then had a large impact on the world.  I
can think of one: Stallman's promotion of free software relied
heavily on an ethical argument (combined with Stallman's
willingness and ability to write good code).  Specifically, he
argued that the ownership of software should be regarded in the
same way that ownership of human being is regarded, and the
latter is surely an ethical argument.  Although Perens and
Raymond's "open-source movement" contradicted Stallman's ethical
argument (it is not unethical to own software, they said, but
there are excellent practical reasons to elect not to own it or
more precisely not to enforce all your rights as an owner"),
Perens and Raymond's practical argument would never have appeared
credible to, e.g., businessmen had not Stallman's ethical
argument motivated thousands of programmer to elect to contribute
to free software in the 14 years between when Stallman started
publishing on free software and when Perens and Raymond started
publishing on open-source software.

Of course Stallman's ethical argument is not capable of causing
an increase in violence, but I see no reason that the internet
could not be used to disseminate ethical arguments that are.

>Needless, I hope, to say: I think of this hypothesis as likely, not  
>because I want it to be true or find such prospects appealing

Same here.

I am thinking of a mechanism by which the internet will probably
decrease violence, but I expect it to exert its effect more
slowly than the mechanisms Zooko and I have described.