Rónán Mullen might be accused of many things – and, over the years, his critics on the left have accused him of a great number of things – but there is no doubting his unfailing manners.  Mullen smiles his way into Beacon Studios on Baggot Street in Dublin to record his podcast with The Currency, all handshakes and pleasantries. He has just come from the Seanad, where he has sat since 2007 as an independent Senator representing the National University of Ireland (NUI) constituency, and, later in the evening, he is joining friends for a musical. “I should have got…