Prior studies have provided evidence of discrimination between drivers and passengers in the context of ridehailing. This paper extends prior research by investigating passenger-to-passenger discriminatory attitudes in the context of ridesharing. This paper 1) examines the variations in class- and race-related discriminatory attitudes between fellow passengers based on their demographic, social and economic characteristics; and 2) tests the impact of one's generic social dominance orientation on discriminatory attitudes in the ridesharing context. To that end, this paper uses data from a survey of 1110 TNC users to create two structural equation models. We find that discriminatory attitudes toward passengers of differing class and race in the shared ride are positively correlated with respondents that are male and older, as well as women with children. Black respondents are less likely to hold discriminatory attitudes with regard to race, while white respondents in majority white counties are more likely to hold such attitudes. Higher-income respondents appear marginally more likely to hold discriminatory attitudes regarding class, but no effect is observed regarding racial preferences. We find that one's generic social dominance orientation strongly influences his/her discriminatory attitudes in ridesharing, supporting the claim that behavior in shared mobility platforms reflects long-standing social dominance attitudes. Further research is required to determine whether these platforms exacerbate or mitigate such attitudes.