Thomas Merton, O.C.S.O., was an American Catholic writer, theologian and mystic. A Trappist monk of the Abbey of Gethsemani, Kentucky, he was a poet, social activist, and student of comparative religion. source
You can get really left of centre influences in mainstream pop. Michael Jackson and Prince are some of the most progressive artists ever if you actually dissect their songs there's some crazy stuff going on.