When "being transphobic" is used to mean "supports transgender people and custom pronouns but objects to one specific pronoun due to his interpretation of gramm

When "being transphobic" is used to mean "supports transgender people and custom pronouns but objects to one specific pronoun due to his interpretation of grammatical rules" (while a dictionary result for "transphobic" says "having or showing a dislike of or prejudice against transsexual or transgender people"), then, yeah, "being transphobic" is not especially bad and arguably not bad at all. In which case it's quite easy for "making a false and professionally-damaging claim" to be worse than that. I'll also note the redirection rhetoric (the subject was a criticism of the open letter).