I read the letter and much of the research the author of that letter supposedly used for the evidence they cite.
The evidence on sexual violence against women and transgender people comes from several different studies, most of which are based on American data, but the numbers are compared between studies with different methodologies. It's quite possible that the numbers are not comparable (a bit like adding pounds and ounces to kilos and grams without realising that one is doing that).
The ones about violence against trans people are not based on statistical samples but on asking people to participate by leaving ads on various transgender or LGBTetc sites.
That is a convenient way of reaching respondents, but because they self-select it is quite likely that their situation cannot be generalised into all transgender people's experiences, say. Those with strongest feelings about the topic of some study are most likely to take part, to give one example of the kind of bias that might be introduced.
So I wouldn't regard the evidence the letter quotes as necessarily correct yet.
But what really struck me about the tone of the letter is something I have felt in other contexts, too: The younger generation appears to feel that they must pick either supporting transgender people or supporting bog-standard women, and they believe the former need that support more.
What they don't seem to see is that they are not supporting transgender people as much as the gender identity ideology with its attempts to entirely erase the sex class 'women' while keeping the sex class 'men' intact. It's possible to support transgender rights without supporting the idiotic gender identity cult, and I'd recommend trying to distinguish between the two as the gender identity approach is inherently sexist, misogynist and ultimately incapable of guaranteeing equality of the sexes (not interested in that, either, of course).