Previous research has established that the success of strikes, and social movements more broadly, depends on their ability to garner support from the public. However, there is scant published research investigating the response of the public to strike action by healthcare workers. In this study, we address this gap through a study of public responses to UK nursing strikes in 2022-2023, using a data set drawn from Twitter of more than 2300 publicly available tweets. We focus on negative tweets, investigating which societal discourses social media users draw on to oppose strike action by nurses. Using a combination of corpus-based approaches and discourse analysis, we identified five categories of opposition: (i) discourse discrediting nurses; (ii) discourse discrediting strikes by nurses; (iii) discourse on the National Health System; (iv) discourse about the fairness of strikers' demands and (v) discourse about potential harmful impact. Our findings show how social media users operationalise wider societal discourses about the nursing profession (e.g., associations with care, gender, vocation and sacrifice) as well as recent crises such as the Covid-19 pandemic to justify their opposition. The results also provide valuable insights into misconceptions about nursing, strike action and patient harm, which can inform strategies for public communication.