You have a good point, but I think there are two other factors here.

One is consistency of enforcement. As the article pointed out, some ideas displayed on posters seem to be more equal than others. The second is that this is a university, not an office building, and the bar for squelching individual expression (at least in my opinion) should be a lot higher.

I used to work at Stanford, and many of the academic office doors were practically bulletin boards. I saw a lot of things I found offensive, but I would never have asked to have them removed. I saw a lot of things I thought were pretty cool, too.

P.S. you can edit posts and comments after they're posted. The editing on this system is very robust.