Asian Americans became targets of increasingly hostile behavior during the COVID-19 pandemic. What motivated this? Fears of contagion arising from a behavioral immune system (BIS) may have motivated differential treatment towards Chinese-born US residents, especially early in the pandemic and among those vulnerable to COVID-19. On the other hand, rhetoric from right-wing media figures may have legitimated anti-Asian behavior. We explore these questions using a behavioral game with a representative sample of Americans at two points: in spring and fall 2020. Participants were partnered with a US- or Chinese-born US resident. The average American treated Chinese-born US residents worse compared to US-born residents in the spring but not the fall, when China was no longer a COVID-19 hotspot. But among Republicans, likely more receptive to right-wing rhetoric, unequal treatment was both stronger in the spring and persisted into the fall.