You use the phrase ‘queer the pitch’ to explain the act of ruining, interfering with, or even completely spoiling something, usually related to business.
Example in use: “Jack was just getting into his call to action when someone in the audience started shouting in an attempt to queer the pitch.”
Sometime around 1812, people started to use the term "queer" as a synonym for "ruin." An example can be found in statements like "the milk's gone queer," which describes spoilt milk. It's not exactly clear when the term "queer the pitch" came into use as an idiom.