The same goes for North Korea, but what do you suggest? A more aggresive stance? The problem with your analogy, is that the person coming over wants the inviter to change his ways. In this case, it is to stop the production of nuclear weapons. With this, you are having inspection teams walking into a country and poking around (it would be like the invitee in your analogy telling the homeowner "oh, your colour on the walls is terrible, you should repaint it" and then the homeowner getting upset and going "get the hell out!").

Since Iran is a signatory to the Non-proliferation Treaty, a closer analogy would be a police officer wanting an inspection of the property. At first request, a warrant would be demanded, and a warrant clearly has defined areas for inspection. Now this is going back awhile now, and I am going from memory, but the invasion of Iraq was justified through weapons of mass destruction from rather circumstantial evidence (purchase orders for certain equipment, and that Saddam was not cooperating completely with inspection teams). Refusing inspections because they start to invade a countries sovereignties is normal, and few countries in the world would not be upset. So in order to maintain privacy and a feeling of sovereignty, a nation will only honor the inspections of certain areas.

If the hypothetical police officer had a warrant to inspect the backyard shed for a hydroponics lab, but then proceeded to search the inside of the house (potentially the ceiling cavity), the homeowner would be furious that the police officer broke the warrant and would be forcing the police officer out. Getting back to Iran, you have to remember that the situation is already voliatile, and the US will be wanting to maintain peaceful negotiations there rather than launching an attack (which I will get to this later), so inspection teams do need to maintain a level of respect towards Iran, which potentially hasn't occured and has aggrovated the situation. For example, if an inspection team arrived from China to the US to inspect your Nuclear facilities, then began to show disrespect towards the US, would the response not be the same as Iran with the US? The answer is "yes", because state sovereignty has been disrespected.

Now, the whole point of peacefully negotiating disrarmament and using embargoes, is to persuade complience without resulting in war. As you mentioned, they feel the pressure from the embargoes, which is why the inspection teams are invited into Iran. They do wish to comply with the demands of the international community whilst still persuing their own ambitions, so a balance is currently being sought. Iran wants embargoes lifted, so they invite inspection teams, in order to ensure continuing embargoes, inspection teams must be sent on request or routinely. If Iran was to request an inspection and an inspection team was not sent because "hey, you didn't cooperate before", then Iran might have a case to have embargoes lifted because the inspection teams are now not cooperating (Iran: "We try and comply, but the US won't check out our progress...how can we change the situation?!". US: "We don't care").

Without inspections, there is only one answer, forceful invasion of Iran. From comments above, why would the US now change their stance which would negatively affect them also? War means expenditure, both money and lives, potential for political instability (it would potentially cause issues with the US self governance of their own nuclear arsenal, as well as domestic issues with the US involved in another war), and also when trade embargoes are clearly achieving the desired outcome. Inspections are being refused, because I am sure they are starting to uncover problems when the inspection teams arrive. From here, Iran, trying to save their own "face", will kill the inspection teams out so not to look weak. They will then comply to the inspection teams worries, and then reinvite them back. The same process happened with Iraq I believe, and no WMD's were located. The whole process is a show of power on both sides, and the current process is far more cost effective than the alternative. Let them have their dance, results are actually being achieved.

Still, my points still remain. It is a show of power, whilst feeling the pressure of trade embargoes and wanting to comply. Iran is becoming less and less of a threat every day. Also, how can inspection teams identify weaponised plutonium if they are refused entry into the country?

I am going to have to research exactly what happened with the inspection teams arent I? Also, I have class in 30 minutes and I haven't eaten yet