I'd lay the blame for the infighting on transphobia, cisnormativity, and basically the whole procrustean gender system.
Some specific ways that the transphobia, etc., in society lead to infighting among trans people:
1. We are all saturated with cisnormative and transphobic ideas and prejudices (not to mention racist, sexist, ....) Trans people (usually) manage to reject -- or rather, come up with narratives that contradict -- those ideas, etc., that cause them individually the most pain, but there are all those other ideas, etc., floating around. And the supposedly rejected/contradicted ideas have a nasty habit of coming back, sort of like the Terminator.
2. As a result of the trauma trans people suffer due to all that transphobia, etc., they tend to be more easily triggered. Not only by the sort of transphobic things that come out of us when we least expect it, but also by the narratives that other trans people come up with to deal with the external and internalized transphobia they experience.
3. Trans people are constantly being threatened by cis society, and hope that they can at least count on other trans people not to do anything they would find hurtful. So when (inevitably), trans person A does or says something that triggers or hurts trans person B, person B is going to feel betrayed much more than they might if some random cis person had said/done it.
I suspect that if, someday, trans people are finally free of internalized transphobia and have healed the wounds that external transphobia has caused, we won't see these divisions. Of course, by then transphobia, etc., will be historical curiosities, to be found only in the dustbin of history, and we won't need so much solidarity.
tl;dr: ya can't win.
In the meantime, I hope we can be gentle with one another. As they say about Sendmail (and RFC's in general): be conservative in what you send, and liberal in what you accept.