My rationale for using the Irish passport is that it reduces the level of investment I need to make to visit a country that has a magnificent reputation in welcoming visitors at the “Joe Public” level and has some interesting, to me at least, architecture and history. If I were to travel on my British passport I would firstly have to pay to have a guide and be limited to where I were to stay - they get to choose the hotels, etc.

As you say whatever the reality of your political / religious beliefs you are likely to be viewed through a particular lens by host nations political infrastructure based on your nationality - hence choosing use the lower profile nationality as it is likely to lead to less formal contact with the powers that be.

There have been few, if any reports, of non-Iranian nationals getting hassle from Iranian authorities that I am aware of. Please note that I am aware of a couple of dual nationality British-Iranians that have fallen foul of the Iranian authorities and I do not make light of their plight (unlike the pillock that is currently the British Prime Minister who single handedly managed to double the prison sentence for a British-Iranian woman). The biggest problem is that Iran does not recognise the second nationality of a dual national and so does not allow consular visits etc.