and I would never amuse myself at a cocktail party in ways that I thought had more than an infinitesimal chance of harming them.

Your ethical intent sounds fine but that is of limited use without competence. The sort of casual disclosure described in the ancestor anecdote would make me slightly downgrade my evaluation of the trustworthiness and social competence of any professional that works with sensitive information. Much like those observed casually gossiping about other people at inappropriate times will be silently downgraded as potential confidants.

If you prefer your advocates to go beyond a principle of 'do no harm'

The overwhelming majority of minor ethical transgressions that we make will "do no harm". Some do. If the consequences were that easy to predict we wouldn't need ethical inhibitions in the first place.