Feminists and other proponents of engineering diversity often encounter resistance to initiatives and programs intended to increase diversity in engineering. Supporters of diversity often suggest both strategies for attracting underrepresented group members and changes to engineering itself. It is less common for proponents of diversity to directly address the stubborn resistance to diversity that frequently prevails in the discipline. This paper addresses resistance to diversity in engineering education using a psychodynamic approach to group social identity. From a group-psychodynamic perspective, resistance to diversity as threatening to the group and to its identity is predictable, although the particular circumstances and culture of the group remain to be analyzed. We give particular attention to the role of engineering "leaders" in influencing group responses to the perceived diversity threat, suggesting a number of practical changes in engineering culture that are likely to mitigate the sense of threat associated with increasing diversification.