One of several things that’s gone wrong with this debate already is that to the extent that you care about the possibility of Iran acquiring a nuclear bomb you should become more inclined to favor bombing Iran. The presupposition there is that bombing Iran will prevent Iran from building a nuclear bomb.
There is, however, no reason to believe this. The correct calculation is that you need to consider how much the damage done will set the Iranian nuclear program back — X. Then you need to subtract from X how much the program will be speeded-up by the political empowerment of Iranian hawks likely to increase funding for the program. Then you need to further subtract from X how much the program will be speeded-up by decreased levels of international cooperation in preventing Iran from getting a nuclear bomb. This second point is crucial. The reason Iran doesn’t have a bomb today is that it’s hard to buy or make the stuff you need to get the job done. How hard this is has everything to do with how seriously a whole bunch of countries — basically all the nuclear countries (Russia, China, India, Pakistan) plus all the right countries (Japan, Taiwan, South Korea, Australia, Canada, Western Europe) — take the job of preventing Iran from acquiring the relevant material.
Right now, these countries are taking that job quite seriously. In the past, they’ve taken it less seriously. In the future, they may take it even less seriously. At the moment, one of the main reasons the world is doing a very good job on this front is precisely because they don’t want to see anything crazy happen. Something crazy like the United States or Israel with US support, launching a clearly illegal, unprovoked war against Iran. Launch the war, and part of the incentive to clamp down on Iran goes the other way. And what’s more, sponsoring acts of unchecked aggression are just the kind of thing that makes other states and foreign populations disinclined to police their own commerce in support of your security agenda.
In short, bombing Iran and the following cycle of retaliation and counter-retaliation, will certainly lead to a lot of people dying. It will certainly lead to lost arms. Severed legs. Severe scarring. Bad burns. Mothers weeping for their dead children. Children weeping for their dead fathers. Houses destroyed and damaged. Permanent hearing loss induced by deafening noises. People go blind. People will be brain damaged by head trauma. That we know. The odds of a diplomatic resolution to the various issues in the US-Iranian bilateral relationship ever emerging will almost certainly plummet. And as a bonus, it might delay Iran’s acquisition of a nuclear bomb by a quantity of time that’s both unknown and unknowable, or else it might speed said acquisition up.