There is a huge difference between the expressed expectation, that a "regime" will come down and a call for genocide. Like this it was presented in the mainstream western media.
There are many governments in the world that do not recognize each other: Western Germany for example did not recognize East Germany, China does not recognize Taiwan, the US has a whole list of states where they desire "regime change" ...

For a full translation of the speech that turned somehow into "wipe of the map":
What he really said

You can also find a comprehensive discussion of this issue at wikipedia:
whatīs going on here?

Here you can also find out more about the official position towards Israel:

Quote:


Iran's stated policy on Israel is to urge a one-state solution through a countrywide referendum. Juan Cole and others interpret Ahmadinejad's statements to be an endorsement of the one-state solution, in which a government would be elected that all Palestinians and all Israelis would jointly vote for; which would normally be an end to the "Zionist state".

In November 2005 Iran's supreme leader Ayatollah Khamenei, rejecting any attack on Israel, called for a referendum in Palestine:
We hold a fair and logical stance on the issue of Palestine. Several decades ago, Egyptian statesman Gamal Abdel Nasser, who was the most popular Arab personality, stated in his slogans that the Egyptians would throw the Jewish usurpers of Palestine into the sea. Some years later, Saddam Hussein, the most hated Arab figure, said that he would put half of the Palestinian land on fire. But we would not approve of either of these two remarks. We believe, according to our Islamic principles, that neither throwing the Jews into the sea nor putting the Palestinian land on fire is logical and reasonable. Our position is that the Palestinian people should regain their rights. Palestine belongs to Palestinians, and the fate of Palestine should also be determined by the Palestinian people. The issue of Palestine is a criterion for judging how truthful those claiming to support democracy and human rights are in their claims. The Islamic Republic of Iran has presented a fair and logical solution to this issue. We have suggested that all native Palestinians, whether they are Muslims, Christians or Jews, should be allowed to take part in a general referendum before the eyes of the world and decide on a Palestinian government. Any government that is the result of this referendum will be a legitimate government.




Well I know that it is hard to believe, that something, that is repeated over and over again might not be true. In German TV it was handled in a very similar way as in Canada or the US. Whoīs to blame for this? Maybe a stupid translator, maybe a superficial and hysterical media? I donīt know. Itīs one of the reasons, why I prefer to use the www and multiple sources.

I do not want to imply, that Iran and Israel have warm relations at the moment, but it should also be mentioned in this context, that Israel and the US had a desire for regime change in Teheran long before Mahmoud Ahmadinedjad came to power.
This is from an article, published in 2003:

Quote:


In fact, right-wing Israelis and their advocates in Washington consider the ayatollahs' Iran a more dangerous enemy than Saddam Hussein's Iraq. Last November Sharon, in an exclusive interview with the Times of London, described the Islamic Republic as "a center of world terror" and openly called upon the United States and Britain to "attack Iran once they are finished with Iraq."[...]
The only conceivable way to overthrow the Islamic regime through external military force is to invade Iran with hundreds of thousands of troops. Only the United States has such a capacity, and Sharon is hoping to persuade President Bush to undertake the mission while his forces are in the region--preferably "the day after" he "finishes off Saddam Hussein," he told the Times. Ranan Lurie, a senior associate at the Center for Strategic and International Studies in Washington, approvingly explains Sharon's argument for popular audiences as follows:

It is inconceivable that [the US] will attack Iraq, succeed, destroy its unconventional laboratories and arsenal, come home for a ticker-tape parade on Wilshire Boulevard and go to the beaches while Iran is still there. Imagine a brain surgeon penetrating the skull of a patient who has two malignant tumors and yet extracting only one of them. Logic says that, as long as you are in that skull, the same incision should serve for the removal of the second tumor.




article

So my personal conclusion is, that the Iranians feel threatened by the US and Israel, and make loud noises in order to appear at least a little bit more dangerous.
About the nuclear issue: itīs an excellent rallying point in government propaganda. This programm, started a long time ago by the Shah, is in Iran a matter of national pride.
Ahmadinedjad is a populist and of course he can exploit the situation like this: the evil US doesnīt want us to become a rich and prosperous nation, itīs the US, thatīs to blame for all economic shortcomings.
Finally: The real world is not a black_or_white issue. Just look at this colorful