Deterrent? A deterrent for what?

In the course of reviewing Michael Quinlan's Thinking About Nuclear Weapons, this Times Of London article includes a paragraph which caught my eye:

It is laughable to suggest that, for instance, unilateral British nuclear disarmament would persuade others to follow our virtuous example. Israelis and Pakistanis, and for that matter Iranians, want ultimate deterrents for their own reasons.

Of those three nations, Iran is the only one which does not seek a nuclear "deterrent". Their avowed aim (as the article goes on to state) is not deterrence, but offensive capability, to wipe out the Jews from the Middle East. Indeed, some commentators have claimed that the threat of nuclear retaliation does not scare the mullahs, as it would only amount to a martyrdom which they actively seek, even if only for their own hapless subjects.