The Gadfly's behaviour seemed to him an absurd piece of affectation, and he was annoyed that Gemma should have been tactless enough to follow his example.
Some political analysts have ridiculed Trump's hopes of becoming the Republican Party's nominee because of his tactless remarks and brash manner, as well as his lack of a clear political program.
To say that a work colleague is a bit of a David Brent isn't merely to point out that they're tactless and insecure-- it's also to re-frame those failings.
Kaethe suddenly realized her error, but she had taken a tactless course and there was no choice but to answer as Nicole pursued her with reiterated questions: " . . . then why were you sorry" ?