Context can affect sexist content. Sure. I just don't think lampshades are a kind of context that tends to increase sexist content, for reasons described above. If one wants to make what one says more sexist, one can accompany it with action (particular or over time), or elaborate on any potentially sexism-free components of one's utterance in such a way that they can now be interpreted as sexist where before they were innocuous. Acknowledging that there already existed a particular sexist interpretation of a statement makes that sexism consciously accessible when it might not have been, but doesn't make it greater in magnitude.