There’s no moral difference between Iran bombing LNG facilities, oil refineries, or aluminum smelters, and the U.S. and Israel attacking gas fields, oil facilities, and steel plants, presuming the attacks are on the facilities of a nation party to the conflict. If one side is engaged in ‘terror bombing’ by striking such industrial targets, both are.
The Gulf countries hosting U.S. forces and allowing use of their infrastructure and airspace to attack Iran are not ‘third parties’ in the sense that they aren’t parties to the conflict. If they let the U.S. launch attacks from their soil, they’re belligerents.
The Iranian regime is evil. That does not, however, mean that anything and everything they do in this war is going to be inherently offside.
Attacking a country that has not allowed U.S. or Israeli basing or overflight is attacking a neutral third party.