It's more that if the saudis are defeated then the route to the holy cities is open to Iran. I do not think Iran will openly attack the cities with e.g. air strikes or missles, that would instantly ruin their PR. But it's more what happens when they actually gain control.We have seen how they treat others who are not from their group when they gain power. Muslims die, our women are raped, our children are killed, they abuse figures äwho we hold dear and Islam is silenced & their jewish origin religion is promoted. We've seen what their militias do in Iraq and Syria, it would be no different in Arabia.
I am not interested in a turkish-arab squabble and I support neither in that kind of war. Turks have good characteristics and so do arabs, I find it frustrating they are divided like this. I would not support a saudi attack on Turkey. Pakistanis are generally a very turk friendly people anyway, most would not support it.
Once these ayotollahs are done with arabs, they will come for me and you too.