Polite but malicious

Politeness 1 is often seen as counteracting what is known as “impoliteness” in people. Implicit in this duality is an automatic projection of malice (ie., “feelings of discomfort, disharmony and even revenge” referred to below) onto the “impolite” (regardless of actual malice being felt by the latter), while masking of the same if it exists in the “polite” (see the ‘ripples’ phenomenon in S.N.A.G. for an example).

This duality is an illusion that many people suffer from. People who are not particularly acting polite (according to whatever cultural norms) are not necessarily “impolite” (aka. “rude”), for they can also be underpolite. Unlike impoliteness (with its implicit projected “rudeness”), underpoliteness involves no malice on the underpolite.

I propose to establish another variety 2 of impoliteness, namely “underpoliteness”. This is impoliteness exercised without malice or spite which occasionally appears to be incidental and a result of socializing habits. Nevertheless, similar to other types of rudeness it creates feelings of discomfort, disharmony and even revenge.

[..] Underpoliteness could therefore, be defined as communicative acts which may cause offense though not triggered by malice.

Example of being polite-but-malicious

From https://lukeplant.me.uk/blog/posts/why-im-leaving-elm/

The leadership style in Elm is extremely aggressive and authoritarian.

By that I do not mean impolite or rude. It is almost always very civil. But still ultimately aggressive and controlling.

The team [at NoRedInk] shows a bewildering mix of cargo-cult inclusiveness coupled with inability to consider that anyone could be different from them in any way that matters.

From https://news.ycombinator.com/item?id=34746161

the core team has that “happy cult” vibe where they think that if they’re (passive-aggressively) polite enough, they don’t have to worry about anyone’s opinion outside their insular little group.

“Happy cult” vibe is exactly how describe that faux-niceness they throw around.

See also

It tends to be more of a trait in Occidental than Oriental cultures. It originated (and arguably still is) as a marker of the upper class. See also Victorian morality.
While the author calls it “another variety of impoliteness”, I’d personally like to keep both distinct. Politeness, impoliteness and underpoliteness form three distinct corners of a triangle. Only two corners can exhibit malice.
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