There has been a long battle between Iran and Arab oil states countries over the name of the gulf that they surround. Saudi Arabia and its Arab allies call it the Arabian Gulf, while Iran and most of the rest of the world call it the Persian Gulf.
This conflict gets personal.
Iran is hosting some sporting events in coming weeks where Arab states will compete, and people who want to popularize the name "Persian Gulf" are going to hang banners to bug the Arab sports teams and players. Arab delegations have also been harassed with these taunts.
Here's one of the banners, shown by Al Arabiya:
I didn't even know Iran had any golf courses!
This is not a unique case of "Persian Golf" sightings. See this webpage and this Facebook page made by overzealous but spelling-impaired Iranians with the same slogan.
The extreme touchiness over this issue has been noted here before.