If someone is uncomfortable with the subject, they probably shouldn't have offered to be on the panel. [And that's not applicable only to this subject.]

Just as men have to take some of the responsibility for doing feminist work and addressing those issues, as white people have to take much of the responsibility for fighting racism, cisgendered people have to take some of the responsibility for dealing with trans people and your concerns. If an individual isn't going to do that, for any number of reasons, zie should get out of the way of those who will do. (Or if zie isn't going to do all of that--I'm both white and cisgendered, but a chunk of my energy goes to the fights that feel closest to me, including feminism and queer issues, and another chunk goes to the day-to-day stuff.)