Perhaps the 'humour' comes from seeing you get cross over their childish antics. Perhaps they see it as a game, like a rather nasty school playground game, and have not thought through how you might be hurt by this.

Another person might see it as an admittedly rather puerile, workplace camaraderie sort of thing and laugh with them, and thereby disarm them, saying, with a grin, something like, 'OK you bustards you got me this time'. They will like you better for it. Sometimes even the mightiest oak has to sway with the wind (I am quite pleased with that lyrical touch).