Isolating people from external points of view is how abusive partners and cults maintain control over the victims. If such a person/organization lets their battered spouses or indoctrinated teens talk to “the outside” they risk questions that lead to answers they don’t want. If you find someone in your life demanding you disconnect from others, immediately take a long hard look at why they are pressuring you that way. People who genuinely want the best for others and try to be part of that aren’t afraid to operate “in the open” under scrutiny.
To be clear, I’m not saying a healthy relationship has to constantly air out dirty laundry as it were, just that forced isolation is a huge red flag.