Why should Israel attack Iran now? Because one day Iran will have nuclear weapons that might be used to attack Israel.
Does Iran have such deliverable weapons now? No.
If Israel attacks Iran now, does that mean Iran would never get nuclear weapons? No, it would merely postpone that outcome for at most a year or two more than it would take otherwise. And then it would ensure an all-out, endless bloody war thereafter.
If Israel attacks Iranian nuclear installations, would that ensure future peace between the two countries? Would it make it less likely that the Tehran regime uses such weapons to strike at Israel in the future? No. On the contrary, it would have the exact opposite effect. Again, it would ensure direct warfare between the two countries and make Iran’s use of nuclear weapons against Israel 100 percent probable.
Why is this different from Israeli attacks on Iraqi and Syrian nuclear facilities? Because in those cases a single strike by a small number of planes would be sufficient to destroy a single building. And the two regimes, precisely because of the strategic situation, would and could not respond. And if you believe Iran’s regime to be so totally irrational, then factor that point into how it would respond to a direct attack like that.
If Israel attacks Iran, would it have backing from anyone else in the world? No, in fact the United States strongly opposes such an operation. Iranian retaliation against oil shipping and terrorist attacks would lead (not overly brave and already appeasement-oriented) Western governments to blame Israel, not Iran. Launching such an attack would ensure a level of international isolation for Israel far higher than what exists today. The idea that a U.S. withdrawal from Iraq makes an Israeli attack more attractive is absurd. U.S. forces and interests are in the Gulf and an Israeli attack would — according to the Obama administration — endanger U.S. interests there.