My mother had a knack for triangulating people through toxic secrets. She learned the behavior from her mother. She would start out by dropping some heavy piece of information that as a child I had no business knowing, and then say, "Don't tell your (dad, brother, teacher, grandma, etc.) because I don't wan't to upset them."
Essentially, this meant I was screwed. Not only was the information itself a source of stress, but I also had to worry that whatever it was didn't leak out. Even if it didn't say anything, if the person found out, I would be blamed and deemed "untrustworthy." On top of all that was an ethical dilemma. The person my mother was keeping secrets from had a right to know. When they inevitably would find out that I kept the information from them, they would be upset with me, not my mom. The stress piled up, and I suffocated under its toxic weight.
Because of toxic secrets in my family, I was psychologically and sexually abused. Because of toxic secrets in my family, I was alienated from all emotional support. Because of toxic secrets in my family, I am an orphan by choice.
Today, I adamantly refuse to keep toxic secrets. I will stay mum about birthday surprises and Christmas presents, but I will not be silent about someone's dysfunctional behavior. Most toxic people have been relinquished from my inner circle, but it's impossible to fully insulate from everyone. Sometimes their poor choices will leak over to me and affect me by proxy. I realize this issue of secret-keeping effects me more than most. It's the fallout of complex trauma. Just like a recovering alcoholic needs to avoid situations with social drinking, I need to avoid "every day" toxic situations, especially anything that starts out with, "Don't tell so-and-so, but..."
The thing is, whatever the secret is that the toxic person is keeping from others is usually minimal compared to the drama they create by preventing it from airing out naturally. Toxic people never seem to trust that other people can handle plain, naked truth. It's a weird, back-handed, co-dependent, passive-aggressive maneuver designed to control and manipulate others. It inevitably backfires, and when it does, it destroys relationships. It's a compulsion to protect themselves from consequences. It's a compulsion to put a buffer between them and reality. A toxic person will fight to keep their secret, when all that energy would be put to much better use toward finding a solution.
Secrets by design keep other people at an arm's length when relationally, they most need to be drawn in. Telling the truth requires strength of character and vulnerability. It means risking intimacy. When someone is surrounded by dysfunction, it's easy to see why secret-keeping looks like the better choice. But keeping secrets doesn't make problems go away. It makes healthy people go away.