One major problem with bombing Iran as a means of disarming them, is that even if we bomb Iran this won't prevent them from building a nuclear weapon. But it seems John Bolton has answered this objection:
If successful, such highly risky and deeply unattractive air strikes or sabotage will not resolve the Iranian nuclear crisis. But they have the potential to buy considerable time, thereby putting that critical asset back on our side of the ledger rather than on Iran’s.
With whatever time is bought, we may be able to effect regime change in Tehran, or at least get the process underway.
Justin Logan points out some of the serious problems with this strategy but it's worth also noting that it's really hard to say whether or not bombing Iran would really delay anything at all. You can think of the timeline as driven by a few different variables. Destroying some equipment and infrastructure and killing some people would definitely be a setback for the program. But an American bombing raid might lead the Iranian government to boost funding for the program. It might lead the Iranian government to restart work on weaponization. It might lead foreign countries to look more sympathetically on the Iranian predicament and become less helpful to efforts to prevent Iran from getting a nuke. For all we know, airstrikes could make the Iranians get a nuclear weapon sooner by making us look like an irrational actor that needs to be balanced against.
Now maybe not, maybe it really would produce a delay and maybe that delay could somehow be used to locate the regime change pony and maybe the new regime in Iran would have no interest in nuclear weapons, but that's an awfully long string of "maybes" to use as a pretext for starting a war.