Agree. They should’ve allowed for more discussion before sending invitations and more effort should've been made to come to a mutually beneficial solution. But going from an invited keynote (great honor) to an invited talk (honor) is not what I would call a deliberate attempt to "disgrace one of the experts in my field." It’s a single track conference where the speaker would be heard by all attendees and could’ve championed his ideas to the larger Rust community.