A nuclear Iran would eventually lead to a nuclear middle east, including all the ISIS and Al Qaeda types, which would be extremely dangerous for the whole world. Better not to have any nukes in the whole region. The good thing is that both countries can totally disrupt each other even without nukes. So, I believe, a stable but competitive equilibrium would/will eventually reach on its own, if external forces stop bringing fuel to the fire.

I have worked with many Israelis and Iranians... and I can hardly tell them apart. At least the ones in the US think almost exactly alike. And from my perspective neither are actually very religious.