Chess.com has been zapping political/religious topics since the site began. It's not censorship that is causing the perceived decline in the forums. It's the people who post in the forums.
Incidenlly, https://www.chess.com/groups/home/open-discussion is available to discuss just about any topic and has been functional since 2008.
Chess.com advertises: "We are social". People should be able to discuss what they like within reason.