UPDATE 1-RenTech's Mercer to step down from fund, talks politics in letter

(Recasts, adds details from letter, byline)

BOSTON, Nov 2 (Reuters) - Hedge fund manager Robert Mercer, a major backer of conservative causes, said on Thursday he plans to step down as co-chief executive of Renaissance Technologies and will sell his stake in right-wing news outlet Breitbart News to his daughters.

Mercer, a wealthy investor who spent decades working behind the scenes in conservative politics, made headlines by providing financial support to Donald Trumps presidential campaign. He and his daughter, Rebekah, advised Trumps campaign and suggested it hire Steve Bannon and Kellyanne Conway who both joined the new administration.

In a letter sent to investors and seen by Reuters, Mercer, 71, said he will hand the reins to co-Chief Executive Peter Brown, 62, in January.

"My goal is simply to explain my thinking, the very essence of which is that all of us should think for ourselves," he said in the letter, outlining some of his thoughts about the current U.S. political scene.

He said he supports conservatives who favor smaller, less powerful government because he thinks society can advance more effectively when people make their own decisions.

He also took a stance against discrimination in the letter.

"Discrimination on the basis of race, ethnicity, gender, creed, or anything of that sort is abhorrent to me. But more than that, it is ignorant," he wrote.

He also hit back against allegations that his politics mirror those of Bannon, Trump's former chief strategist. Bannon, the executive chairman of Breitbart, was seen as helping shape the president's populist voice and left the White House in August.

"I have great respect for Mr. Bannon, and from time to time I do discuss politics with him. However, I make my own decisions with respect to whom I support politically. Those decisions do not always align with Mr. Bannon's," Mercer wrote.

Mercer also said he has no plans to retire and plans to continue working at Renaissance, which oversees roughly $50 billion, and focuses on research. (Reporting by Svea Herbst-Bayliss; Editing by Tom Brown)