I am not a friend of the Iranian REGIME, they are as you pointed out fundamentalists and a destabilizing factor in the region. What I disagree on is that they are lunatics who would actually use the bomb. The Soviets and the Americans never used nuclear weapons precisely because they are a defensive and not an aggressive weapon. Without this deterrent power the place where I am living, central Europe, might have been the battleground of WWIII.
Same with Pakistan (besides Saudi-Arabia the hotbed of Sunni extremism and the place where the US fights right now against them; Afghanistan is basically just a backyard) and India or Israel and Iran. The logic of mutually assured destruction still works.
If Netanjahu may have the bomb I fail to see why Ahmadinejad many not have it (ignoring for the moment that Khamenei would actually wield the power) as well. They are both populists with some fundamentalist background but their game is all about the money.
It's like with George W. Bush, easy for any Arab media outlet to portray him as a crusader with Blackwater and so on but in the end the Iraq war was not a crusade (OK, it was definitely a a bit off a "we are a dieing empire but don't fuck with us" message) but a scam to rip off the American public and let corporations like Halliburton profit enormously.
No terror-supporting state ruled by religious reactionaries and fundamentalists should have the bomb.
Please note that I don't wanna bash anybody, certainly not the US or Israel which are lovely countries, but as I wrote above it is easy to claim that Bush and Netanjahu were respectively are associated with religious fundamentalism. Yet they have behaved respectively do behave rationally and do not cause a nuclear holocaust.
So yeah, without being a friend of the influence that Iran has in the region, particular in Lebanon via the Hezbollah, in Palestine via the Hamas and now in Iraq (which has a Shiite majority so I am happy that they are no longer oppressed by Saddam but the little Kissinger in me wonders why we got rid off Saddam whom we installed after all in the first place as a bulwark against the mullahs) I wholeheartedly say that if the Iranians develop the bomb we have nothing to worry about.