How can the American public be led into another war over possible WMD? What makes this palatable and how is it at all believable? I see four reasons:
2. Perceived moral clarity
3. Factual Ambiguity
4. Historical amnesia
The driving force behind conflict with Iran is fear. Fear that Iran will get the bomb. Fear that Iran will bomb Israel. Fear that Iran will bomb US troops in Afghanistan. Fear of the unpredictability of Ahmadinejad and Khamenei. Ultimately, fear of the Iranians, period.
Iran isn't on par with North Korea, but it certainly is painted as reclusive and as a closed society by the media. "Iran" conjures images of Ayatollah Khomeini, hostages, the crackdown on the Green movement, of Ahmadinejad (in his ever-present Borat-esque gray suit and white shirt) calling for the destruction of Israel, and of religious fanatics. All these images instill fear.
Fear can lead people to do stupid things and sometimes can lead them to do heroic things. However, the line between the two is often blurred. Going to war can be seen as heroic, but it can shortly be recognized as a colossally stupid endeavor.
Moral clarity, in regards to the US, is important to the conflict as well. To the average American's perspective, this is clearly a conflict between good (us!) and evil (them!). Unlike the war in the former Yugoslavia for example, where both sides committed horrible crimes, this conflict is perfectly clear cut: The Iranians won't let inspectors in; the Iranians are the ones calling for the annihilation of another country; the Iranians are imprisoning protesters; the Iranians are not agreeing to talks about their nuclear program.
In the interest of a balance in perspective, consider this: The US's refusal to allow troops to be tried by international bodies for war crimes; John McCain singing "Bomb Iran" to a group of veterans; Guantanamo Bay; and the Bush policy of explicitly not negotiating with Iran. It's a matter of perspective. Moral clarity fades when considered from both perspectives. Vietnam taught us that.
Also consider the ambiguity of the situation. We are being told that the US and Israel should bomb Iran because of its nuclear "ambitions". Really? That's enough evidence to start a war with? The exact same argument was used with the war in Iraq and we all know how well that war was sold to the US public. I'm thinking that the CIA should be on its guard if a request comes through to prove that there are WMD in Iran, because that's what got them in trouble last time. If there is evidence, double check it ("Curveball" anybody?). My feeling is that is exactly what has happened, hence Washington's placing the ball in Israel's court. If Israel does strike, I doubt it would have genuine US government support-- but Washington will probably go along with it anyway.
The facts are not solid and the cause not well defined. Ambiguity allows us to fill in the details ourselves with our imaginations, and not have to deal with nasty little facts instead.
Lastly, as mentioned, starting a war over the possibility of Iran having WMD is the exact same reason given for the war in Iraq. That is not being mentioned nearly enough in the public "debate". America should have collectively rolled our eyes when we heard that this was reason enough to go to war. "Hidden nukes? Gimme a break." But, no. This isn't a part of the discussion. And that, my friends, is historical amnesia. And that is sad.