Queer somebody’s pitch
To queer somebody’s pitch is to spoil their chances of success and dates in this figurative sense from the late 18th/early 19th century. The sense of pitch used here derives from the practice of street or market traders during the late 18th century who operated from a piece of ground called a pitch. These traders would sometimes try to spoil the efforts of competitive traders by shouting them down and denigrating their offerings and hence ‘queering their pitch’. ‘Queer’ here means to spoil and dates in this sense from the late 18th century and has nothing to do with ‘queer’ as in homosexual. The phrase ‘sales pitch’ meaning a verbal selling strategy derives from the same sense of pitch.