Updated

A controversial senior analyst with the liberal activist group Media Matters is leaving the organization to start his own blog, saying he doesn't want his criticism of Israel to "harm" Media Matters.

MJ Rosenberg, who also got into hot water for mistakenly accusing the Drudge Report website of racism in coverage of the Trayvon Martin case, announced Friday on the Media Matters website that he was "striking out on my own with a brand new website and blog."

"My presence here is being used in an effort to shut Media Matters up," Rosenberg said in announcing he will be creating a new site, MJayRosenberg.com.

Rosenberg tweeted an apology to Matt Drudge last week after calling Drudge "racist" and accusing him of using a phony photo of Trayvon Martin "for incitement purposes.”

Martin, an unarmed Florida 17-year-old, was killed in February by a neighborhood watch volunteer, George Zimmerman, who said he shot Martin in self defense.

Drudge's website other media sites had posted a photo of Martin sporting a tank top, looking noticeably older and bigger than he appears in a photograph widely carried by media outlets that have reported on the story.

Rosenberg's apology said he had mixed up Drudge's photo with one used on the website of Michelle Malkin that was incorrectly identified as the shooting victim.

Harvard Professor Alan Dershowitz has branded Rosenberg an anti-Semite for branding pro-Israel Americans with the name “Israel-firsters.” Dershowitz, a lifelong Democrat, has called on the Democratic Party to distance itself from Media Matters. Rosenberg responded to Dershowitz by telling him to “go to Hell” and urging Dershowitz’s students to boycott his class.