Obsequious (adj.) or obsequiousness(n.) literally means acting overly polite, but it often has the connotation of excessive or feigned politeness. Merriam-Webster, "obsequious":
: marked by or exhibiting a fawning attentiveness
One of the example sentences illustrates how obsequious can be used in a context to suggest insincerity:
The obsequious villagers touched their caps but sneered behind her back. — "George Sand," 1980, in V. S. Pritchett: A Man of Letters, 1985
The OED ("obsequious, adj.," def. 2a) also has an example that pairs obsequious with dishonest and other adjectives:
1993 Poets & Writers Sept. 27/1 Most had been alienated by boastful, dishonest, obsequious, cloying and, occasionally, nonexistent letters.
Then this recent news story shares a similar sense that obsequiousness is less sincere or desirable than "unfailingly helpful and polite" (Lopez, Shelley. "Alisa Duke selected as Max Carraway Employee of the Year." FSU News, 22 Sept. 2022, https://news.fsu.edu/news/university-news/2022/09/22/alisa-duke-selected-as-max-carraway-employee-of-the-year/):
“Ms. Duke is unfailingly helpful and polite, without being obsequious,” said Shi-Ling Hsu, the D’Alemberte Professor in the College of Law.
It's not quite the perfect word - someone can be obsequious without putting you down - but it's the word I'd use to describe politeness that felt purely performative but insincere.