How can it lead to harm? In what way are they going to be harmed?
As I said, unless you are in an environment that is very accepting of trans and non-gender binary people, then being forced to use the wrong bathroom could result in the trans/non-gender binary person being harassed or worse. How is that hard to understand? It can 'out' people that don't want to be out, it can send a message to them they their is something wrong with them (thus potentially physiological harm, particularly for kids that are trans), or just in general draw unwanted attention just because they need to use the bathroom. For example, a trans-man would probably blend in more in the men's restroom, and a trans-women would probably blend in more in the women's restroom.
Because the argument above is completely subjective without an example of how someone would be harrassed, and honestly in comparison the world still addressing, feminism inequality, northern and southern conflict still continuing within USA despite the slave war ending many many years ago, refugees of syria, and i'm sure many other issues, that i'll be frank, need addressing much more than 'I want to wear a dress when I take a crap without being judge'.
You are basically countering stupid bills with melodramatic statements of individual bathrooms everywhere without cubicals, and that gender specific toilets cause harm to the trans people, which are not a race. Lifestyle, god giving them the wrong body, mental handicap, disability handicap, gene issues, whatever you wan to believe, but they are not a race of people.
The arguments you suggest do not fix nor progress trans gender, and the arguments you give appear to be strictly emotively given without research or discussion, which Ironic considering gender is being considered a grey aspect rather than one or the other, but good and bad is final, it's a very christian thinking.
Point is this discussion is kind of pointless other than to seek oppinions of others, but if you do not like them nor accept them, then what do you want?