What image is this?

An incompetent writer who mixes metaphors with idiotic abandon.

I suppose the sniff could be a sniff of disdain.

I have trouble anyone sitting and sniffing with disdain--or even a runny nose-- while being actively assulted.

I agree with Contrex that the use of metaphor in the sentence under consideration is impossibly sloppy. However, sitting back (pulling away) and sniffing are still gestures that suggest rejection and disdain.