[markc]

I'd imagine that increasing friendliness in such a situation could easily be interpreted as mocking or patronizing (no matter how sincere you are) and in that case the hostile reaction isn't to the friendliness it's to the mis-perception of it.

[zem]

in most cases it is patronising; that's the entire point of how you psychologically "win" the encounter by being friendly to someone who is being a jerk to you.

[marvin]

...which is why using social manipulation techniques like these area great for working with strangers or people you will never see again, but mostly a bad idea in more permanent relationships. E.g. with colleagues, repeat customers that you want to see again etc.