There is a growing body of scholarship in science education that attends to the role of affect as shaping youths' negotiation of and experiences with disciplinary science practices. As part of the special issue Centering Affect and Emotion Toward Justice and Dignity in Science Education, in this paper we examine how power and affect shape epistemic negotiations as youth and adults designed a community survey during a 7th grade biology unit on stress. We used interaction analysis methods to examine how care for the survey takers co-operatively emerged as an epistemic ideal when creating a community ethnography. The epistemic ideal was shaped by disrupting disciplinary practices, negotiating multidirectional powered adult-youth relations in the classroom, and youths' positionings in relation with macro-sociopolitical worlds. How youth characterized care was not neutral but involved youth experiencing politicized empathy towards survey takers coupled with them taking action against survey takers potentially experiencing harm through a tool of Eurocentric science (i.e., the survey). Overall, this work contributes to a critically nuanced understanding of how affect is entangled with and visible through the complex powered dynamics that youth and adults negotiate when engaging in sociopolitical allyship towards more just ways of knowing, examined through the emergence of epistemic ideals within an explicitly justice-oriented middle school science curriculum.