My apologies for not answering these posts individually.
In my view, a policy that says you must always use someone's preferred pronouns in every situation would not be discriminatory but it may be unreasonable. However, a policy that says you must not, in most situations, use pronouns for an individual that they find offensive is, in my view, neither discriminatory nor unreasonable. It isn't forcing you to refer to Upton as "she", but it is saying you shouldn't refer to him as "he" in most situations if you are one of his work colleagues.
I agree that Upton is a "he". I think I have consistently referred to him as such on these threads. I don't care whether he finds that offensive. I'm not talking to him and I don't work with him. However, if talking to him or in his presence I would either avoid pronouns altogether, use gender-neutral pronouns or, if there really was no other option, refer to him as "she" (unless it was a situation where it was essential for me to use male pronouns in order for my meaning to be clear, e.g. explaining why he isn't allowed in the women's changing room). Yes, I know he isn't a "she", but I don't need to be deliberately offensive to him. I wouldn't be comfortable calling him "she". There would be a certain amount of cognitive dissonance going on. But I can accept a certain amount of discomfort in order to avoid offending others. And I would only use "she" as a last resort, when there was no other way of avoiding calling him "he".
As far as the courts are concerned, it is reasonable for an employer to want employees to avoid being offensive to each other. An employer will want a harmonious workplace. If I was a colleague of Upton's, since I can navigate most conversations without referring to him using either male of female pronouns, it would not be unreasonable of my employer to expect me to do so and to avoid referring to him using male pronouns in most situations. It would, however, be unreasonable for them to insist I use female pronouns for Upton in situations where I could avoid using any pronouns or could use gender-neutral pronouns, or that I use female pronouns in situations where use of male pronouns is necessary to make my meaning clear. If, for example, I go to HR to complain that there is a man using the female changing rooms, I can clearly refer to Upton using male pronouns in that situation as attempting to use female pronouns would render my complaint meaningless.
I don't like the way TRAs are trying to force people to use pronouns in a certain way. I do not support that. And I would like to see pronouns reclaimed so that woman always means biological woman (and biological woman does not mean what Upton thinks it means). But I don't think the courts are the way to do it.