Not many people believe a man who says he is a woman, of course.
TERFism is a confusion of competing agendas. Let me explain -
TERFs can't recognise transgender people, or intersex, it demolishes their raison d'etre. To recognise that transgender people and intersex babies are born would reduce their belief to pure unadulterated bigotry. They would be left with pure Radical Feminism.
In their quest for taking apart the value systems, that they perceive had imprisoned them in the patriarchal society, they seek comfort in a higher position in the food chain. In this process they are not only accepting that the system exists, they are seeking to insert their new found higher status into that social system of inequality, which they are now content to accept. They are seeking to gain some improved position in society, higher than another group, by denying that the group that they choose to compete with, actually exists.
In the process of fighting for improved social status for women, they shift, conflate and confuse the real origin of the danger to women, i.e. close male relatives and partners.
They are, rightly, highlighting a real and ever present problem, safety for and of women, but they are focusing their fear in the wrong places and on the wrong people.
The danger is, according to all available data and statistics, primarily from close male relatives and partners.
In their befuddled quest for their improved status in society, they focus on those that, according to data and statistics, present no danger to women.
Women have never felt more in danger, especially from cyber sexual harassment, and it's exactly the same origin of, and degree as risk of physical danger.
So TERFism is a befuddled mess of competing agendas a) it practices and teaches inequality, while striving for improved status for women in what they perceive as an unequal society, and b) it shifts the focus of the real problem for women's safety to the wrong origin, essentially masking that real origin of the danger.