Acting as if what someone says isn't what they mean but hides some kind of deeper terrible motive is one of the tactics used by abusers who coercively control their victims. Also tactics used in situations like McCarthyism, the cultural revolution, witch trials etc. Where people are judged to be bad based on no evidence just because the accuser says so.
E.g. you may have SAID 'Do you want tea/ there are two sexes in all mammals' but what you MEANT (you WITCH!) was 'I hate you / I hate all transpeople'. This false equivalence is an attempt to apply coercive control and to shame, undermine and hurt the victim and categorise them as worthy of punishment (even if they've really done nothing wrong).
Claiming there is widespread transphobia on Mumsnet is abusive to the women being accused. I personally experience this as abusive and harassing.
Given this is a forum where there are many women trying to escape abusive relationships, this is particularly unethical. It may also constitute bullying and harassment - baselessly accusing Jo Phoenix of 'transphobia' was found to constitute harassment in a court of law.
It is interesting that 'linguistic transphobia' is not defined in the event that was cancelled. You'd think that would be step one.
And let's remember that eminent paediatrician Hiliary Cass has been accused of 'transphobia' for doing her job. And has received threats that mean she's been advised not to use public transport. I.e. suffered real harm and danger.
This abuse of language is not ok, particularly in one studying linguistics for chrissake. The casual application of the term 'transphobia' to women who are advocating for women's rights is not ok. It is abusive.
I think it's important in this context to remember in particular transwidows and the transwidows threads on here. It's bad enough just tarring all women on here with the same slur, but blanket accusing transwidows of 'transphobia' is really really terrible behaviour.