Before I go on, I'd like to say this:
The government of Iran is a horrible, evil, anti-Semitic radical regime. I acknowledge that they are trying to get nuclear weapons, and not for peaceful purposes. I do not believe it should be allowed to have nuclear weapons.
However, invading Iran and establishing a democratic government would cost the US and the West so much more than it would benefit us. And I'm not implying that the US could not overthrow the Ayatollah-we could capture Tehran by the summer.
However, history is repeating itself. Just as we fear that Iran is creating weapons of mass destruction, we feared the same from Iraq during the 1990s and early 2000s.
One could argue that as we justly invaded Afghanistan to destroy al-Qaeda, we should invade Iran to destroy their weapons of mass destruction and prevent them from falling in the hands of terrorists. Iran does have connections with terrorists, and if not al-Qaeda it's confirmed that they are in league with Syria and other terrorist groups who, with a nuclear weapon would wipe Israel off the map.
But what's the difference between al-Qaeda and the government of Iran? Al-Qaeda and other terrorist groups exist only to destroy their enemies; namely the US and Europe. That's why we were justified in invading their strongholds in Afghanistan. Their raison d'etre was to destroy us, so we had to invade and stop them.
But Iran? They're no friend of the US or the West, but their reason to be isn't to destroy us. It's to control and subjugate the people of Iran. Our only problem is with the weapons they're trying to create.
Our solution to a nuclear-to-be Iran is to do what we did with Iraq before 2003.
1: Send in UN weapons inspectors and make sure Iran cooperates
2: Bomb any nuclear facilities in Iran.
3: If need be, create a no-fly zone with the support of local Arab nations (Saudi Arabia would be happy to help)
The way to deal with an Iran that wants nukes is to prevent them from building nuclear weapons, but the key is to leave their government intact.
Now there are some who want to invade Iran, and they may ask these questions:
If we overthrow Iran's government they'll stop making nuclear weapons
True, but then we'll have another mess on our hands. Iran may be a terrible government, but they're not going to hand over power to Al-Qaeda or another terrorist group that isn't bound by international treaties or the UN.
Iran's government wants to hand over nuclear weapons; if they somehow get one it will fall into the hands of the terrorists
A valid fear, however, Iran is not going to hand over a nuke to al-Qaeda or Hamas anytime soon, and here's why: Iran's
government is self-preserving. You can't just give, let alone make, a nuclear weapon to someone without there being a trail. If Iran gave a nuclear weapon to a terrorist and that terrorist used it, Iran would be found out and there would be worldwide-sanctioned invasion and regime change for Iran. Khomeini may hate the US and Israel, but he's not going to trade being Supreme Leader for anything.
Getting rid of Iran's dictatorial government will bring democracy to the Middle East.
Not really. We're still having trouble with Afghanistan, and Iraq wasn't much of a success. There's more al-Qaeda than ever in Iraq, even before Saddam. The fact is, sometimes people aren't ready for democracy and the Middle East sure isn't. One thing we've learned from Iraq is that sometimes it's better to have a stable enemy country than an unstable ally. If we want to get rid of Iran's nuclear weapons we'll have silos to bomb and scientists to kill; a clear chain of command to target. With terrorist groups like al-Qaeda who live in caves and are more ragtag bands of thugs than armies, it's difficult to track them.
In short, the problem isn't Iran's government: it is the weapons themselves. Don't invade Iran-we'll get another quagmire like Iraq. Use missile strikes, bombings, and covert methods to ensure that Iran doesn't get nukes.