Most of the "we need to sniff out which people aren't trans enough" sentiment seems to go along with a naive idea that trans people will never hurt you, which, like I see how people get there, they spend years or decades being abused by cis people and unable to find trans community, they spend this time building up an unhealthy rose-tinted idea of what an all-trans space will finally be like. And then once they get there and it's full of people being people and it isn't some kind of frictionless utopia their response to being hurt by another trans person tends to be either 1) this person must be egregiously evil and must be hunted down to the ends of the earth or 2) this person must not be actually trans, and should be kept out of all trans spaces. Understandable trauma response, but if you find yourself carrying it out you should still sit down and shut up before you make everything worse.
Because yeah the "trans people are harmless" mentality tends to also coincide with either "I don't have to worry about hurting other people cause I'm trans" or else constant self-doubt about whether you are virtuous enough to be actually trans. Deeply sad and unserious, and we give this sentiment way too much leeway.
Notably this shit seems way more common among white trans people than trans poc, perhaps because of a lack of experience with what it really means to live and interact with similarly-marginalized people. And like have them be messy and complicated without being ontologically evil or "the oppressor".
