In his essay, Mr Marshall highlighted the absurdity of being labelled a fascist when 13 of his family members were killed by the far-right during the Holocaust.
He said: “My Grandma, unlike her cousins, aunts and uncles, survived. She and I were close. My family knows the evils of fascism painfully well. To say the least. To call me ‘fascist’ was ludicrous beyond belief.”
Despite initially only taking a step back from the indie band, Mr Marshall wrote that now “the only way forward for me is to leave.”
He said: “I hope in distancing myself from them I am able to speak my mind without them suffering the consequences. I leave with love in my heart and I wish those three boys nothing but the best.”