Venture capitalist Steve Jurvetson fired back at his former DFJ partners and denied any sexual harassment on his part, one day after the Silicon Valley firm he co-founded announced he would step down under a “mutual agreement.”In a post on Facebook Mr. Jurvetson said Tuesday he left DFJ, also known as Draper Fisher Jurvetson, following a collapse of “interpersonal dynamics” with his partners. He said an investigation that the firm launched into misconduct allegations three months ago tore the firm into factions.