Okay so here's the thing. As far as the trans hatred goes.
Cisgender people, mainly heterosexual, but yes indeed also gay and lesbian and bisexual, tend to view their genitals as encapsulating their gender. Ie for men, the penis is the ultimate sign of manhood, and for women the vagina is the ultimate sign of femininity.
Transgender people flip this concept on its head and it cuts these cis people right to the quick. They can't conceptualise that gender isn't what is between your legs, rather it is a way of existing. This then threatens their respective masculinity/femininity as if a trans man can be a man without a penis, what on earth does that mean for us with penises? Has our masculinity been reduced to nothing? Back in our day if you had a penis you were a man, as simple as that!
There is also the age old issue of (mostly) cis straight men taking issue with trans people in what eventually comes to light as transmisogyny (the intersection between transphobia and misogyny that specifically trans women face, often violent) and these cis het men are usually the ones who are most vocal about demanding that all trans people out themselves, disclose their genitals, and ask whatever questions about their junk they're asked. The main reason for all of this is because while cis het men love *their own* penises, they are loathe to even be seen standing near another man's naked schlong (or woman's, in this case) so they become paranoid about trans people because if trans people are able to end up passing well and having surgery and going on hormones and looking like any other cis person (especially trans women) then how on earth are these men supposed to make sure that the sexy lady they just wolf whistled at and checked out walking down the street isn't packing a huge dick? Cause that makes them gay, remember? Therefore if we make all trans people disclose their status and reframe trans women as men (which means that sex with them is now gay, just like we wanted) and trans men as women, we can sleep easy at night because our sense of comfort about our precious sexuality hasn't been disturbed.
It's for some of these reasons, and many, many more, that people hide behind transphobia. They often use the same tired old defences to their arguments as well. They claim all transgender people play the victim card all the time, of which the outcome is that when they *do* say something highly transphobic and the trans person rightfully calls them out, they can point the finger and go 'ha, see! Playing the victim again!' and they get away with it every time. So utterly predictable. Or they use their primary school education about biology when they've never even heard of intersex people to tell trans people that they consider them their assigned gender at birth regardless of how successful a person's transition has been, which is thoroughly idiotic because I can't remember the last time I've know anyone who owns a magical chromosome detector they can carry in their pocket.
One of the absolute favourite lines of the standard transphobe to play is the 'no one wants to date/fuck a tranny' line, whereby they create this mystical alternative reality where they know a bunch of trans people who are all sad and miserable because they are perpetually alone and unfuckable, even though the vast majority of trans people wouldn't go near these people with a 10 foot pole. Then when a trans person informs them that they have actually had many partners, as have most of their trans friends, and they have no shortage of people wanting to fuck them, they pull the most spectacular mental gymnastics to continue to justify their embarassing beliefs, including telling a person that the men they fucked who identify as gay are bisexual because they fucked them and they're a trans man, so apparently these transphobes now have the ability to change other people's sexuality who they've never met, all because it doesn't fit within their dichotomy of how gay sex = two vaginas or two penises and straight sex = a vagina and a penis. Never mind that plenty of younger people in the world have no issues dating or fucking a trans person, these mid 40 conservatives can't imagine themselves doing it which means no one would.
So it's those reasons, or its usually because I'm a trans guy and I'm far more attractive than cis men are. Which usually gets me the superbly backhanded compliment of 'wow it's so unfair that you're hotter than me and you're trans!' to which I usually respond 'how is that unfair?' and they go 'well I'm cis' and I go 'if you think you're supposed to be hotter just because you're cis you can stop talking to me at any time you ugly fuck. I'm hotter, deal with it.'
Then out comes the 'fuck you, you disgusting mutilated freak tranny whore, I was just being nice to you because no one wants to fuck you on this app. You should be grateful'
And then I tell them that I'm better than them in every way.