When we design assistive robots, we are largely well-intentioned: we want to use our research and engineering skills to help others. However, to meet this end, as we move towards more disability- and social justice-oriented HRI research, it is important to critically examine the dominant social narratives of disability that shape how assistive robots for disabled people are conceptualized, designed, and deployed. In this paper, we introduce the concept of robot-mediated paternalism (RMP), drawing on a multidisciplinary body of literature, including critical HCI and crip technoscience. Then, we discuss how RMP may manifest when assistive robots provide unwanted assistance to disabled people and interfere with their decisions/actions based on assumptions about their autonomy and care needs. Finally, we reflect on and offer actionable suggestions for how HRI researchers might mitigate RMP by aligning their work with the principles of disability justice. Overall, our work advances disability-centered research on assistive robots and, in doing so, supports more equitable, inclusive futures for disabled communities.