I've never seen people on Slashdot, as a group, claim to be open-minded.
The administrators are known to be heavy-handed responding to things they don't like. This gets keeps the dissenting extremists off the system. It also causes an all-around discomfort for people who have something to say, and a general distaste for the system for many(most? all?) other people on the system.
Moderators are often quick to moderate "troll" to anything that might spur disagreement. This prevents flamewars. It also prevents a great deal of insightful discussion, and discourages newbies from participating.
A couple months ago, I lost my moderator priviledges. I've never said anything intentionally inflammatory before on Slashdot, so I don't know for certain what specifically caused the priviledges to be revoked.
Recently, I subscribed to Slashdot. I block all ads, and view 10 ad-free pages per day. I had all the plums at first, but now some of them are gone. For example, I can no longer see articles from "The Mysterious Future," and read Slashdot every fifteen minutes to twenty minutes, for most of the day.
I'm not expecting this account to escape unscathed from this rant, but I don't care. I've been slowly maturing beyond the community fascism for a while, and I guess it's time to move on.