How about not being able to be kicked out of your apartment or get fired from your job because they find out you're trans?
As in many of such issues, its far more complicated than it seems. Certainly there are few cases in which people do that just out of pure antipathy and disgust towards transgender people.
But equally certainly there are also many more gray area cases. Like people that do it because of more or less accurate stereotypes of risks involved in dealing with such people. Say, in case of apartments, its fairly well known, and in some areas probably very accurate too, that there is a disproportionate risk that the trans tenant to be is going to lead unusually vivacious lifestyle of some kind that will get the neighbors to complain or call the cops all the time.
Perhaps not. But the owner is aware of the risk and may be willing to take it... or perhaps have another, less risky tenant available. Or worse yet, rumors or warning signs of this kind of problems are already out there. Or just simply its one of those non-passing trans cases that's just gonna make the neighbors uncomfortable, which may also impact the owner and his business in a meaningful way.
And speaking of that, this is an even more of a potential issue in workplaces. A lot of them have dress and grooming codes, sometimes quite strict, and sometimes for a good reason. They consider it absolutely unacceptable to look like a freak. Many won't even allow you to look like a perfectly average working class t-shirt+jeans dude. Nevermind, say, a member of metalhead subculture walking around the office and dealing with customers with unkempt long hair, three day stubble, wearing an unzipped black leather jacket presenting some suitably edgy band shirt.
Why is that so? These workplaces are very much insistent on "professional" corporate look, yadda yadda, and especially about not making customers and coworkers uncomfortable by workers looking like freaks, such rules sometimes being strict to quite extreme and hard to justify degrees.
On the other hand, the T lobby argues that there should be an exception to the "no looking like a freak" rules (formal or informal) for their social group, so that even the worst cases of "IT'S MA'AM!" should be immune from this kind of scrutiny, regardless of the practical effect they threaten to have on perceptions of the business, likely to far worse degree than the abovementioned metalhead.
Is this fairness? Is this justice? Why should some identities be more important than others, as in, protected? And why should these be the alphabet soup ones and not others?
That goes into the appropriateness of the whole concept of "protected classes" and "protected characteristics", which in hindsight perhaps aren't a good idea at all.
Of course the lobby for said identity would, at least at first, use the least controversial examples to push their case, but as their political influence rises and broadly worded laws are introduced, suddenly it turns out that these protections will also be used, or you could say abused, by the gray area cases, and if feeling secure enough, the lobby will stand behind them too, and claim that the laws protecting these is a feature, not a bug that prompts for exceptions to the laws.
How very dare they...