ESPN host Keith Olbermann was temporarily taken off the air in February after fighting with Penn State fans on Twitter. Olbermann, who has a long history of being combative with Twitter users, called one fan a “moron” and said all Penn State fans were “pitiful” after a misunderstanding that occurred over a Penn State fundraiser.

In an appearance on The Late Show with David Letterman, Olbermann said that he assumed someone was tweeting something negative at him — sparking the arguments with followers — when actually someone was sharing a harmless link.

“I got into a dispute with some folks on Twitter and it got personal because on Twitter you don’t think of anybody else as an actual human being, just as something, somebody you have to bury. Or they’re going to bury you. And you subtract yourself from the human race and just start going after people and you can do really stupid things, and I retweeted something that was about my charitable cause. I assumed it was negative — I didnt read, it was a link to a website. I just went back at somebody and they weren’t even throwing punches.

So I ended up sending out what read as a tweet that was somehow opposed to pediatric cancer research. To St. Jude’s, and to Make-A-Wish in the last six years I’ve made like 200 donations. These are my causes. So my horror at this when the folks at ESPN said ‘tell you what, just stay home a couple days, let’s let it cool down’ I said ‘thank you.'”

Since the incident, Olbermann hasn’t sent a single direct message to another user on Twitter.