Story highlights Rap Genius co-founder made insensitive comments about killer's manifesto

Mahbod Moghadam called Elliot Rodger's writing "beautiful"

He also speculated on the sex appeal of Rodger's sister

Rap Genius CEO: "I cannot let him jeopardize the Rap Genius mission"

The co-founder of Rap Genius, an online-annotation website, has been fired after marking up the 137-page manifesto of California killer Elliot Rodger with comments that are being called tasteless and creepy.

Mahbod Moghadam used his site, which lets users post notes interpreting rap and hip-hop lyrics, to comment on Rodger's exhaustive autobiography, which includes his reasons for killing six people in Santa Barbara, California, on Friday before apparently turning a gun on himself.

In more than one note, Moghadam called Rodger's writing "beautiful," and in another he speculated on the attractiveness of Rodger's sister.

In a journal and in a video posted online, Rodger had expressed frustrations about not finding women to date and resentment toward couples who kissed in front of him.

He also wrote that his anger toward women intensified after he overheard his sister having sex with her boyfriend. "MY GUESS: his sister is smokin hot," Moghadam wrote.

Moghadam also made comments about a girl Rodger described as the only female his age he ever saw naked.

"Maddy will go on to attend USC and become a spoiled hottie," Moghadam wrote, before adding, "This is an artful sentence, beautifully written... ."

Rap Genius has removed the notations. But they were captured and reposted online by Gawker Re/code and other news sites.

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On Monday, Rap Genius co-founder and CEO Tom Lehman released a written statement saying that Moghadam had resigned.

"Mahbod Moghadam, one of my co-founders, annotated the piece with annotations that not only didn't attempt to enhance anyone's understanding of the text, but went beyond that into gleeful insensitivity and misogyny," he wrote. "All of which is contrary to everything we're trying to accomplish at Rap Genius."

Lehman continued: "Mahbod is my friend. He's a brilliant, creative, complicated person with a ton of love in his heart. Without Mahbod Rap Genius would not exist, and I am grateful for all he has done to help Rap Genius succeed.

"But I cannot let him compromise the Rap Genius mission -- a mission that remains almost as delicate and inchoate as it was when we three founders decided to devote our lives to it almost 5 years ago."

Lehman said the site, which describes its mission as helping users "discover the meaning of rap lyrics," decided to post Rodger's writings in hopes that users' annotations "will eventually be a good resource for people looking to understand this tragedy."

Part One of Rodger's writings currently appears on Rap Genius between breakdowns of the lyrics to "Believe Me" by Lil Wayne and John Legend's "All Of Me."

As is frequently the case in today's digital world, the social-media backlash against Moghadam's comments was fast and brutal.

"Appalling use of technology by already questionable behaving site," Re/code co-executive editor Kara Swisher wrote on Twitter with a link to that site's story.

"What's most newsworthy about the story of the Rap Genius founder isn't that he was fired but that he didn't think his words were wrong," tweeted author and tech journalist Ed Bott.

Observers also criticized Moghadam's own Twitter feed , which features many posts that could be viewed as crude at best and sexist at worst.

On Monday, Moghadam took to Twitter to beg forgiveness for his comments.