Iranians see Saudis as 7th century AD invaders that destroyed their Sassanian Empire with their Muslim conquest and tried to Arabize them. Some Iranians insist that Arabs tried to remove their Persian language and did in fact take their women. This is seen as a great tragedy in Iran’s long, illustrious history, and something that they’ll never forget. Though they accepted Islam and reinvented it in the form of Shia Islam, Iranians began a movement to reassert Iranian identity and resist attempts to impose Arab culture.
Aggression between the regime of Saddam Hussein of Iraq into Iran did not help matters and war ensued in 1980. There was an alleged use of chemical weapons by Hussein leaving many Iranian military and civilians dead.
There is contention over the name of the Persian Gulf, with Saudis preferring to rename it to the Gulf of Arabia as well.
Gulf Arabs are viewed as desert dwellers, inferior, less cultured, Wahhabi Islamists, savages by most Iranians. Arabs are referred to as locust eaters and lizards negatively in Iran.
Portrayals of Arabs are virtually negative as well, showing the darkest Arabs they can find, with the biggest noses making evil grimaces, while their Persian nationalist post images that portray mostly fair-skinned people smiling, although they have some people with deeper skin as as well and some have robust noses.
Saudis similarly dislike Iran in my opinion, but don't go through all the hoopla trying to smear or distance them on social media; one might say they'll use politics. They have worked with the US and Israel to have the US pull out of the Iran nuclear deal, and announce the further sanctions against Iran to the pleasure of Israel. Iran and Saudi Arabia are orchestrating turmoil and controlling local actors in the Middle East. They’re inflaming sectarian conflicts to gain power. The purpose of these moves and the US-Israel-Saudi coalition is to cripple Iran's economy and weaken the country.
Gulf Arabs may use negative language when referring to Persians as well, calling them fire worshipers, where Shiite Islam is seen to be a foreign and deviant form of Islam. Some Gulf Arabs may feel superior to Iranians, citing that Islam’s prophet came from Arabia.
Saudis supported Iraq's strongman, Saddam Hussein, whom they felt kept Iran's influence in check, but when he fell from power, Iraq grew closer to Iranian interests, having a large Shiite base.
As a result, we have Iran and Saudi Arabia fighting a series of cold war and upheavals in countries of the Middle East through proxy wars, instead of fighting directly, pulling in allies like the US and Russia. Examples are Syria, Bahrain, and Yemen. There is speculation that the Saudis would like to see the downfall of Hezbollah, an Iranian backed militia in Lebanon. This could prove devastating for the small country which has seen enough civil war in the past.
In Iran, you have a hardline Revolutionary Guard clique that is trying to assert itself vis-à-vis the pragmatists that have just signed the nuclear deal [with world powers], so they’re trying to assert themselves on the regional front by saying, “We still are a power to be reckoned with.” They’re asserting themselves in these regional conflicts. In Saudi Arabia, there’s this new king ... who is using these regional wars as a way to bolster his bona fides and raise his nationalist profile and build support. We can’t really separate the regional adventurism from the domestic politics of each country.
What Is the Feud Between Iran and Saudi Arabia Really About?
Influence in The Middle East