Israel needs to have them based on simple, undeniable fact that it's neighbours can be and have repeatedly screamed their desire to be an existential threat to Israel's. No one other then lefty useful idiots know that Israel nukes are a defensive weapon of last resort. And I agree with them.
The reasons why Iran should never have nuclear weapons....
..... the stated desire, very public and very well stated desire that they want to have regional hegemony over their neighbours AND by definition, the heart of Western economic power.....oil.
....regional nuclear proliferation.....in the most unstable part of the world.
....the direct threat to Israel. Both verbal and de facto. See Hezbollah.
....the low regard for human lives the mullahs have. All the useful idiots have to do is pick up a book or Gurggle what the imams did in the war with Iraq.
This argument is simple. If Iran has no nuclear ambitions and the imams are sane, then they should submit to nuclear proliferation inspections. If they are as insane as they appear to be, then they should NEVER have any nukes. There is really no argument for NOT dealing with Iran with a heavy hand, including a military one, other then one of appeasement and capitulation to the inevitable.