The names have been changed to protect the clueless.
[person A] To play devil’s advocate here for just a second. I wonder what would have happened if either …
A) attendance to the conference had been by “private invitation only” and kept the agenda private?
B) The organizers had been a women’s poc group to discuss issues affecting them and they had asked for only women of color to attend.
A) would be problematic but not objectionable in the same way as the assertion of “all women are welcome EXCEPT YOU.”
B) is not an applicable comparison. Women of color experience oppression from white women (yes, even you - yes, even me). Cis women do NOT experience oppression from trans women. The “women’s POC group” comparison is a big red herring because it appropriates the idea of safe space - a space where an oppressed group can meet to discuss its issues without the oppressor in the room - and turns it into a weapon against a group that is itself oppressed by the group declaring its need for safe space. An analogy would be a white feminist group declaring that it needed a conference for only “white-born women.”