I also had simular issues with this and asked a simular question on susan a long time ago.
my honest opinion is theres more into it than just so, so theres no simple answer but I have a couple of theories which can play a part.
1) first the diffrent groups in the lgbt+ are pretty diffrent and not always understood of each other.
a gay person may know everything of being gay but not what it like being trans, a trans dont know what it like being asexual, and so on, which can make the same prejugde simple because they dont understand, and because they is in another position of power and priviliged where there not vulnable anymore. (you also see this with mixed discrimination where people who exemple are black and agenst racism can be homophobic, or people who are gay can be transphobic and so on)
the key is simple understanding and being willing to learn about each other, but theres also an issue of diffrence in these privilige I mentioned before. A gay white, cisgender and gender conforming man who is monogamyous romantically and sexual into other men, dose surely not feel the same type of opression as a black, nonbinary trans non-binary guy who is poly, aromantic and asexual. in a way you can say there is a hiracy.
Certain countrys have gained the mark of being "lgbt friendly" but the truth is most are only friendly under certain conditions. such as gay marrige, adoption,permission to transition, and so on.
making a small piece of math saying: understanding of someone diffrent (ex a gay person understand someone trans) + also understanding there position = can be a challenge to get around, specially if you only hang around other gay, trans or whatever you are (people) and don't really care about the others issues.
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then my other theory is simple Fear
I belive alot of the transphobia and so which came out is not just ignorance but simple fear and emotion taking over. I see many people who been put down so much that they now got used to it, both themself and for others that it normal to be threated badly. I also see the other way around people who really do NOT want to be threated badly anymore, yet the fear of it to happent can overtake them.
Exemple I seen many transexual people who are binary who had been discriminated non-binarys.
the reason is simple. they belive that that by viewing non-binary people would think they also are non-binary
and by viewing there non-binary way of seeing gender they are afraid people who is more easly adapted to the binary gender model wont take them serious anymore, and may not deal with them anymore.
another exemple could be a transwomen who is discriminated toward ->-bleeped-<-s because people somethimes think thats what she is, and she fear more acceptance toward ->-bleeped-<-s will gain her less acceptence as a transwomen again = fear.
I seen this alot of time within a minority. gay people looking bad on other gay people for giving a "bad rumour for the gay comunity" and so on. I think it only happent when you are a minority, I mean when was the last time you heard anyone say "she is making such a bad view on the straight people" - for anything a straight person did?
I think maybe it something more or less biological in humans that when you are scared you may react more drastical and harsh than normally. you also see it in how nazism got popular during a time where people was pretty desperate and how neo-nazism is rasing more and specially in the areas with the highest unemployment rates.
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okay enough rample I hope this put some thoughts into it.