Maybe they didn't want kids getting any ideas about contacting demonic entities (Satanic Panic and all that). In the 1970s, the TAS episode "Magicks of Megas-Tu" wasn't shown on some stations for depicting the devil as a good guy.
https://groups.google.com/g/net.startrek/c/3EH3TyJRaLQ?pli=1
https://groups.google.com/g/net.startrek/c/3EH3TyJRaLQ?pli=1
