I remember reading Stephen Covey's The Speed of Trust. He referenced that how you talk about others either builds or breaks trust.
How you talk about others can also impact your social capital. The best examples are from middle school. If you mock someone that everyone else mocks, then you "side" with the mockers rather than the one being mocked, thus using that person as collateral to increase your social standing.
As grownups, the methods are a bit more sophisticated, and still in use--even in the corporate world.
But regardless of how funny, insightful or effective the negative observations, there is no way to guarantee that the person you are sharing with agrees with you. And while they may listen politely, the one sure thing you are doing is creating an impression of yourself. That you are not trustworthy.
Because they know that someone who uses others as social collateral, isn't above using them when their back is turned.
How we speak about others says very little about them and a whole lot about us.
It impacts trust.