Remember we are talking about people that routinely convince others (of their ilk) to strap explosives to themselves and then go blow themselves up in the largest crowd of Israelis they can find. Then pay off the families. There were 19 people that willingly flew aircraft into buildings. They join the American, Afghan (and previously, Iraqi) police and army to conduct suicide attacks on Americans.
And you seriously believe that once they have a working nuke, they are NOT going to use it on Israel? Really?!?!?!
The biggest threat to Iran is clearly not Israel, but the US. The US can go in and accomplish regime change in Iran, if we felt inclined to. The US has been sending drones over Iran, giving their machines STUXNET, and funding/training MEK, which is interested in violently overthrowing the Iranian government. Sure, they deserve it, but there you are - clear evidence of hostile action.
Israel doesn't like Iran, but there's no way in hell they would nuke Iran, as it would just make
everybody in the region clamor for their blood. They'll bomb nuke plants, but they aren't stupid enough to try to do regime change - they don't have what it takes to do so.
ETA: Iran's nukes are to deter the US, not to 'annihilate' Israel.