The harm is that telling people to “assume good intent” is a sign that if they come to you with a concern, you will minimize their feelings, police their reactions, and question their perceptions. It tells marginalized people that you don’t see codes of conduct as tools to address systemic discrimination, but as tools to manage personal conflicts without taking power differences into account. Telling people to “assume good intent” sends a message about whose feelings you plan to center when an issue arises in your community.