The assertion that the emergence of a Preventive State is either necessary or desireable is pernicious. Mr. Dershowitz seems to argue that the prospect of horrors committed by individuals or small groups are more horrible than the atrocities carried out by established governments. I see little evidence of this, given the ability and overly righteous willingness of governments, including the US, to inflict inhumane damage on millions of innocents, whether abroad or at home.
If the consiquenses of a single suicide bomber are so awful, how much more awful is it to kill hundreds of thousands of civilians and create millions of refugees? If it is ethical to establish a Preventive State to prevent inviduals from committing relatively small acts of violence, then surely it is ethical for individuals to prevent governments from unleashing large-scale organzed mass-violence on a country unable to defend itself.
It seems likely that Josef Stalin and Adolph Hitler would also subscribe to the desireablity of establishing a Preventive State.