The present-day Unitarian Universalist Church is well known for wearing its politics on its sleeve; it's left-wing, loud and proud. Combined with the political content of the scene, and recent Trek's unsubtle attempt to make thematic commentary on present-day American politics (see Paths of Disharmony), I find Mr. Mack's characterization attempt unsubtle, overreaching and out of place in Trek.
The funeral occurred in a Unitarian church, yes That's the only content referencing the denomination: all of the thoroughly secular dialogue in that scene was delivered by President Bacco.
I don't know why people choose to take offense from the mentioned existence of something harmless that they dislike for whatever reason. Is difference that frightening?