In pursuing a career, he became a reporter for the Deseret News and continued working for the paper for sixty years, advancing to the position of president and chairman of the board.

[6][7] At Brigham Young University on 27 August 1954, at the Convention of Teachers of Religion on the College Level, Petersen delivered the speech, "Race Problems—As They Affect the Church".

[8][9] The speech outlined the religious underpinnings of racial segregation and supported its continued practice as it related to intermarriage between blacks and whites.

[12] Petersen said: In spite of all he did in the pre-existent life, the Lord is willing, if the Negro accepts the gospel with real, sincere faith, and is really converted, to give him the blessings of baptism and the gift of the Holy Ghost.

In the 1940s, Petersen coined the term "Mormon fundamentalist" to describe people who had left the LDS Church to practice plural marriage.