Your words would be dead on if we were talking about the Soviets, who had cynicism as the fundamental of their Philosophy. But your words capture the Islamists, who have fanaticism as their fundamental, only up to the point of that fanaticism. I think that there are far more absolutely depraved and Hate demented psychos in Islam than anywhere else on earth (and THAT'S saying something) The HATE of the Jew that they haver invited into their souls will drive them to places the Soviets weren't stupid enough to go. Think Hitler.
The fanaticism of the islamic regime is bluster. They are first rank hypocrites and never shy of opportunism.
The mullahs were not reluctant to accept Israeli support versus Saddam Hussein during the Iran-Iraq war.
If only the destruction of Israel were their goal, they wouldn't bother increasing and widening their political networks in Iraq, Afghanistan, Lebanon and Palestine (and overseas). The islamic republic is trying to become a regional great power. Every indicator speaks for this.
That being said... a nuclear Iran will result in every other state in the region arming itself with nukes. This could mean that terrorists one way or the other will get their hands on them. THEN there will be real trouble.
Again, my assertions don't mean that I think mullah nukes aren't a threat. The case for stopping Iran's nuclear program is compelling, but it's well adviced to get an realistic impression of it.