It's actually impossible to communicate the Mysteries verbally anyway, as they are a feeling you experience rather than something you can describe; but trying to describe it often makes the feeling less real because you have distanced yourself from it by describing it.
Details of magical workings performed should be kept completely secret, even from other practitioners, because otherwise the effectiveness of the spell is reduced – it dissipates the energy. Also, once the spell is complete, the group that has worked it should talk about something else and not mention the spell again (otherwise it recalls it).
Knowing when to speak and when not to speak is a normal part of human social intercourse, e.g. When someone asks you if you like their new dress, and the truth is that you hate it, it's best to say something non-committal rather than going into explicit detail about how and why you don't like it. Not long after children learn to speak, they learn when not to speak and develop the important bonding and survival mechanism of sharing or keeping secrets.
Stuff that people reveal about themselves in the intimacy of the group should be confidential. If the group is not competent to deal with someone's trauma, however, extended confidentiality (telling it to a competent professional) might come into play.
Details of rituals should generally not be talked about (except to other Pagans). The main thing here is the principle of "cast not your pearls before swine" - if you make something explicit that was implicit & subtle, it somehow cheapens it or sullies it.
If ever you find yourself in an abusive situation, then tell someone else, get help. If the person concerned is doing something illegal, then tell the police. Don't be swayed by the argument that revealing what they are up to would bring Paganism into disrepute – nefarious activities have a way of being discovered, and then it would be much worse if it looked as if other Pagans were covering up for the miscreant. Also, people are legally and morally obliged to report such matters, otherwise one becomes an accessory to the crime.