When trans people get rejected for jobs that they're eminently qualified for, the reason given usually has to do with "culture fit", "relatability" or some similar bullshit reason. Now, obviously the hiring managers are mostly just lying, but clearly in some cases they're telling the truth, and for some mysterious reason trans people just never fit with their culture. There is, however, only really one thing I can say to that.
If your culture excludes trans people, it's a shitty culture and you need to change it immediately.
Skill
There is no difference in inherent skill between groups with hegemonic power (in this case, mostly straight white men) and those without them: this has been shown over and over again, to the point where I have no intention of re-litigating it. Amazingly enough, this applies to trans people as well, and in the case of trans women and tech, a disproportionate number of engineers are trans women, and an even more disproportionate number of the very best engineers are (this isn't exactly because we're inherently more talented, but the environment is harsh enough that only the best of us are able to stick it out).
So, is maintaining your company culture worth denying yourself some of the best talent in the field? Are you really willing to sacrifice being the best at what you do in the interests of maintaining a culture that you feel comfortable with?
Self-delusion
A common rejoinder to the above is that despite what I've asserted, trans people are somehow worse at engineering than cis white men. Now, this just isn't true. What I would ask, however, is what believing that says about your ability to assess factual information.
If this is the position you take, you've demonstrated that you're completely incapable of actually assessing engineering quality, or, in short, that you can't tell the difference between good and bad work. If you can't identify when a trans woman is a good engineer, what the hell makes you think you can identify when a cis man is? Are you, perhaps, just judging on the basis of people being confident and similar to you in enough ways?
And for that matter, what about choices of technology? If you can't objectively assess whether or not a person is good at their job, what makes you think you've chosen your technologies and platforms well? What's stopping you from being fooled into buying something you don't need by a glib salesman, and then throwing away half a million dollars a year because you were unable to use the tool correctly? What's stopping you from making your entire tech stack way more complicated and way less reliable than it is?
Sure, you're not going to hire every trans person whose CV you get. But if you don't hire some, you are probably committing serious lapses in judgement.
Soft skills
Having dispensed with arguments about technical skill or judgement, the next thing that seems to come up is "soft skills". Apparently we often have trouble communicating or working with people. Well, you can judge my writing for itself to see if that's the case: I'm at least literate, and given the average quality of writing in the corporate world, that's no small thing. But, catty comments aside, let's have a look at that.
The first point to be made here is that communication and teamwork are two-way things: they do not just involve our hypothetical trans person, but require effort from both parties. And, as much as I hate to point this out, if someone thinks you're delusional, mentally ill, depraved or part of a Jewish plot to undermine the west (all things that a depressingly large number of people believe about trans women), communicating or working with a trans person is going to be impossible for them. Blaming the trans person for that is honestly perverse.
Even if things aren't that extreme, a good team with good leaders should be able to communicate and work effectively with a wide range of people. If you can't communicate effectively with people who sit even a little bit outside your company culture, I don't think I want to know how to communicate with clients or stakeholders. Bluntly, communicating with people who are very different from you is a key part of your duties, and if you're failing at that, you're failing at a core aspect of your work.
There is also the fact that you might not be able to identify effective communication or teamwork skills as such. While a lot of trans people are just awkward or shy (and who could blame us) a lot of us are very effective at communicating across precisely the kind of cultural divides that I've described above: it's a core survival skill for us. We're also often quite good at picking up on distress, loneliness and people being excluded or overlooked, and that kind of work is really important to maintain a healthy and effective workplace. Not counting those as soft skills is an unbelievably foolish thing to do.
What's left?
So, if excluding trans people is foolish from both a hard skill and a soft skill perspective, and having a culture that encourages it leads to a culture that systemically makes poor judgements, what's left? What other reasons for maintaining this kind of culture might you have? In many cases, it's simply a matter of comfort and inertia: changing your culture means bringing new and scary people into your business, and it means that you might have to change what you're doing and reflect on your behaviour, both interpersonally and (which is often worse) technically. Rejecting trans people on grounds of culture fit is an act of profound cowardice that does extreme damage to an organisation's culture and ability to do good work. It is an extremely serious issue that needs to be stopped immediately wherever it shows up.