Overdose of arrogance and vanity again. For God's sake, why does the border change or the protection of Azerbaijan upset Iran so deeply? Why doesn't everyone mind their own business? Is it necessary to get permission from Iran when starting a business on the issues between Turkey and Azerbaijan? There was such a "take permission" rule but we forgot?
The principal reason for Iran's behaviour is very much out in the open. For the Iranian regime, there's nothing more dangerous, threatening and alarming than the formation of a transnational ethnic identitiy involving Azeris on both sides of the the Iranian-Azerbaijani border. The Persian-majority establishment fears possible consequences for the state. They believe that showing restraint at this point can lead to an escalation which could easily turn this issue into a matter of life and death for the regime.
Nothing is considered as a greater threat to the Mullah reign - not Israel, the US, the GCC or ISIS - than Turkish/Turkic nationalism. This is why they react so harsh and decisive. On top of this, there is this vague fear that Arab, Turkmen, Kurdish and Baloch people could also question Iran's territorial integrity with neighboring states waiting for the first opportunity to shred Iran into pieces. We often forget that Iran has much more ethnic conflicts lingering under the surface than any other state in the Middle East.
However, there are two points that should not be left out of the equation:
1. Many Iranian Azeris are loyal to the regime which is often overlooked by Turkish and Azeri Pan-Turkists.
2. The number of loyal Iranian citizens with Azeri ethnic background is declining - and the regime forces are fully aware of this development.
During my restricted conversations with Iranians and Iranian Azeris in Western Europe and on the Internet, I could sense that these anti-regime sentiments are actually caused by the overall terrible economic situation in Iran rather than a genuine Azeri nationalism and hatred for Persians.
Right now, things are very blurry and people can't really tell what the future will bring which doesn't help. If anything, it makes all parties more nervous.
However, one thing is for sure, we're at a crossroad and many Azeris in Iran are in a process of "reevaluation".