Trevor points out that a policy of doing nothing is still a policy. Yes! The right one!! My argument was that doing nothing should be the default position that requires very compelling reasons to be overridden. But, even this assumes that we're debating within a framework of comparing costs and benefits (a utilitarian framework), which, when stated explicitly, almost everybody denies they are doing (see points 5 and 6.). I think we have certain rights that may not be overturned by a compelling cost benefit analysis.
An example of this principle that traditional lefties usually accept (and I don't think is much different from other areas we have discussed) is freedom of speech. People defending free speech don't think that every allowed utterance improves society. We know that the right will be used to promote poisonous views, yet the principle of free speech is amazingly well respected in the west. Of course it is periodically challenged by people who think that the harm done by some forms of expression outweighs the benefit of being free to make them. This is a reasonable view, but it is not one that is compatible with the underlying principle (though this is usually denied).
As for me, I don't enter into a cost benefit analysis whenever the argument is presented by the press because of some new outrage.