Sustainable engineering education requires us to address discrimination and inequity of experience, thereby contributing to a renewal of the engineering profession that reflects a rich diversity of experiences and perspectives. Many students experience discriminatory events in their classrooms, however the presence of teaching assistants in relatively high numbers means that they could provide both proactive support and reactive intervention to support inclusion and combat discrimination. This paper examines teaching assistants' (TAs) contributions, employing observations from students (3988), student teaching assistants (277) and doctoral teaching assistants (65). We found that (i) students overwhelmingly reported respectful interactions with their TAs, (ii) while both student assistants and doctoral assistants see inclusion as part of their role, student assistants expressed more confidence in their ability to foster inclusion. Our analysis indicates that TAs are a constructive force to build inclusive engineering classrooms, informing our recommendations for improving campus culture.