We could just say most people "hold ideas that are incompatible with an open society". Look at all the "enlightened free thinkers" in this thread who want it to be illegal to state something they adamantly disbelieve ("hate speech"). They are apparently not aware that the same laws could be brutally used against them, should they ever find themselves disagreeing with the predominant belief system (and newsflash, enlightened free thinkers: a lot of your beliefs already do).

The problem is that the term "open society" has no objective meaning, so you can use it to exclude any set of beliefs that you don't like, up to and including anarchists.