First, it appears Ms. doesn't handle dissent from the preferred line well (updated)

Second, people actually discussing and criticizing their article instead of handing out praise troubles them greatly.
Third, according to this clown Nocera at the NYEffingTimes, it's all the NRA behind it, and we're all bullies and censors.
...But, Kort went on to say, the comments Ms. Magazine had received were almost entirely from pro-gun advocates, and she and the small staff at Ms. were overwhelmed. Instead of leading to a high-minded debate about guns, her blog post had instead attracted insults and vituperation, and a clearly stated desire for “payback.” Other gun blogs had picked up Yewman’s post to mock it or insult it, with many commenters suggesting that the police in her hometown be called about what she was doing. Inevitably, somebody discovered—and posted—Yewman’s address.

What was Kort’s solution to this dilemma? Incredibly, it was to kill the rest of Yewman’s series. “I don’t think I should post the next two installments of this—they’ll only fire up the troops again, and we’re just not equipped to handle this on our blog,” Kort wrote. When I reached out to Kort, suggesting that Ms. had allowed itself to be censored by Second Amendment absolutists, she would not respond on the record. Suffice it to say that Ms. disagrees with this assessment. But I don’t see how you could view it in any other way. Ms. published something the N.R.A.-types didn’t like; they responded by bullying Ms. online, and Ms. folded.
Let's note some things here:
Reasoned Discourse^tm was in full effect: comments that didn't meet what Ms. wanted to see were mostly disappearing into the 'awaiting approval' black hole.
They were surprised that there was criticism and discussion?  Really?
I’ve been super careful NOT to approve any comments that mentioned where you might live.  And yet there her address appeared... made a good excuse to kill the series, didn't it?
Instead of leading to a high-minded debate about guns, her blog post had instead attracted insults and vituperation, and a clearly stated desire for “payback.”  So they say; about comments that nobody got to see, etc.  To me anymore, this falls under the same heading as politicians crying about 'death threats from gun activists': "Let's see them.  And if someone actually threatened you, turn that over to the police.  Have you?"

Very short version: Ms. and Yewman assumed either that they would receive primarily praise and ass-kissing for this series and were shocked when it didn't happen,  or hoped that any criticism would be small in quantity and all of a "look at the hating neanderthals' type.  When neither happened, they couldn't/wouldn't handle it.


From Sebastian:
This is straight from the anti-gun playbook: censor dissenting viewpoints and shut down debate, then claim to be doing it because people who have a pro-Second Amendment viewpoint are nasty brutes who just want to bully and intimidate everyone. That has not been my, or anyone else’s experience anywhere else on the Internet where dialog is not moderated and people are relatively free to have open discussion. Yes, some people on the Internet are poster children for the Greater Internet Fuckwad Theory. This is not news to anyone, and while I support “Ms.” magazine’s editorial discretion, I think bowing out of this is cowardly, and shows they are not committed to having any kind of real discussion on a serious topic.