why didn't de Blanc include Matthias Kirschner, FSFE in open letter?

There is far more evidence concerning Kirschner's behavior towards women.

A female employee engaged a lawyer to tell him not to visit her home

He still came to her home anyway.

http://fsfellowship.eu/matthias-kirschner-jonas-oberg-fsfe-paternity-maternity-hypocrisy/

de Blanc and her enablers choose to attack RMS

They choose not to turn a blind eye to Kirschner, they give him money,
which shows active support for bullying when convenient.