Iran poses no threat today, I agree, but they will pose one once they got nuclear weapons.
Do you have any rational argument to back this up or is this a product of your crystal ball?
If one actually considers actual historical facts regarding events similar to the issue of Iran and nukes, it becomes pretty damn obvious that the acquistion of nuclear weapons tends to politically stablize a country, tends to reduce outward tensions with enemy states and tends to induce a peaceful political engagement with enemy states.
To illustrate this, one only has to look to the Indian sub-continent. India and Pakistan have fought several wars and have a long list of grievances with each other - all in the last 60 years. Once the two powers had a 'nuclear balance' against each other, they stopped going to war at the drop of a hat and started meaningful political engagement with each other.
This is the doctrine of MAD - Mutually Assured Destruction. It is to be noted that the only time a nuclear weapon has ever actually been used in war, it was when one power held a nuclear monopoly. The instant that (US) nuclear monopoly was broken by the USSR, the probability of nuclear war diminished substantially and the probability of peaceful engagement between USSR and USA was increased.
So now, looking at the Middle East, we are faced with a situation where one state holds a regional nuclear monopoly - Israel. This causes political instability and an increased likelihood of war. On this basis, it is entirely reasonable, based on past historical patterns to expect that if/when Iran achieves nuclear weapon power, that will generally act to reduce overall political instability in the Middle East as it has in other previous 'power-rivalries' of our nuclear era.
Iranian nukes would act as a balance of power and reduce the military tension in the Middle East and western governments apparently don't like that one little bit.
Nato's role has been, for the most part, to protect its member aginst nuclear threats.
IMO, they prepare the terrain.
This is totally and completely wrong. The USA has always pushed to make NATO nuclear - it was not meant to be that way.
France officially departed the military arm of NATO in 1967 formally over objections to the US unilateral decision to make 'flexible response' nuclear doctrine substitute for a comprehensive ground defence of all NATO territory.
That is to say, the French objected to the US making nuclear weapons a first line in NATO defence. NATO was meant to be a multinational conventional armed force, not a nuclear umbrella under US whim.