Much research examines citizens' beliefs in misinformation and whether these beliefs can be corrected, but we know far less about how misinformation impacts social attitudes. We propose that misinformation can induce affective shifts that increase out-group animosity and fuel polarization. Politicians amplify these effects by embedding misinformation into larger narratives of threat from out-groups. We conduct a preregistered vignette experiment following the 2021 elections in West Bengal, India, exposing respondents to a misinformation message that invokes salient identity cleavages. We randomize whether citizens are asked about intergroup attitudes before or after exposure to misinformation and find that treated respondents report more hostile out-group attitudes. Corrective information fails to mitigate these negative effects, suggesting that the effects of misinformation may not operate through citizens' factual beliefs. While it is known that directional motives aid the proliferation of misinformation on social media, our study shows that misinformation itself can exacerbate social cleavages.