I do think that Cake at the moment is a bit of an echo chamber.
I think there are two factors which contribute to this.
1. Certain subjects have a higher interest population on Cake. Sort of like going to a place where Sports fanatics hang out and trying to bring up subjects in which sports fans are not interested. In this case, it is a lack of interest in some subjects rather than any opposition to a specific viewpoint.
2, When an overwhelming majority in any environment holds one position it tends to squelch open discussion. There aren't a lot of vocal Republicans in Hollywood as one example. There are some viewpoints which are held by so many Cake participants that this may intimidate those who are not by nature argumentative.