That’s a good question. A hard one to answer, specifically. It’s probably easier to identify things that aren’t reasonable expectations than it is to set clear boundaries as to what is, or are.
Naturally, I think my views, attitudes, and actions in this area, are appropriate. I would (do) call them by their preferred name. I wouldn’t exclude a trans person from my personal circle of friends or family or associations because of their trans status. I wouldn’t shield my children from their existence based on their trans status. I would argue that they should be allowed to marry the person of their preference. I would treat them with the same courtesy, respect, and dignity I afford everyone as a condition of their humanity, only to be revoked if their actions warrant it.
I do not think it’s a reasonable expectation to demand that other people contort their reality to fit the trans person’s view of it, and demand that they be called by whatever pronoun they feel suits them, or to insist that anything short of society identifying and treating them as no different from other members of their chosen gender (reference bathroom/shower facility usage, athletic competitions, etc.) properly defines “transphobia.” And I certainly wouldn’t consider applying the force of law to that agenda via hate crime/speech legislation to be a reasonable action, either.
That’s a general starting point, anyway.
You started off decently enough, but purposely mis-gendering people is transphobic behavior.
