trans people are a threat to the status quo of the patriarchal-capitalist Gender regime. the ideology of patriarchal capitalism is that your gender assigned at birth is immutable and there are only two. in patriarchal capitalism your gender defines a lot of what path your life will take, the societal expectations placed on you, and importantly what opportunities and privileges are afforded to you. obviously the setup is men dominating and oppressing women which has been going on for far longer than capitalism but worsened significantly under it. the division of reproductive labour is the social basis of gender. according to traditional gender roles, women are expected to act as broodmares to reproduce more worker stock and also perform most or all domestic labour in essentially a slave role. the existence of trans and trans nonbinary people disproves the two axioms on which this all rests, that your gender is immutable and one of just two. gender in capitalist ideology is little more than a tool or system of oppression, and by existing and living our lives as we see fit and not railroaded by traditional expectations based on assigned gender at birth, we show clearly that it doesn't have to be that way. so to answer your question they come for us because we are a genuine threat to capitalist patriarchal orthodoxy, we show by our actions and existence that a better social order is possible, one where individuals are actually afforded self-determination instead of being locked into a predetermined role based on what genitalia you are born with.

sorry it's kinda an incoherent thought dump, there is plenty more to say this is just a quickie of the root superstructural reasons that we are perceived as a threat to patriarchal capitalism. of course, most transphobes won't have these specific reasons in mind (in fact probably couldn't comprehend them at all due to ignorance) and have just been convinced by capitalist propaganda and transphobic media to hate us because we are icky etc. the prevalence of misogyny also is why it's so easy to get people to be transphobic, a lot of it just boils down to either "hah! why would a man want to be a woman?", or "hah! a woman could never be a man".