The F-15's which were shot down through friendly fire were in the Air to shoot down Iranian Missiles being fired at US bases. They were defending against Iranian missiles, just like all the other ABM systems of the GCC countries. There is quite a difference between an F-15 taking to the air to defend its base and an F-15 taking to the air to attack Iran!
Even though I am getting tired of repeating myself. The GCC countries are hosting the US for their protection and not for attacks on Iran. It is their soverign decision, right or wrong. And as long as GCC bases are not being used to attack Iran, all Iranian attacks are unjustified and are only being undertaken because Iran neither has the means to hit US mainland nor the technology to target US Aircraft carrier group ships.