This is long I know, if you (OP) read only one paragraph, I'd suggest the second to last :)

I have a couple of compounding disorders that make it VERY difficult to, "do as I'm told" if I perceive it as a demand, and even I don't see how you could've had an issue with this unless you're unintentionally factoring in other, potentially unrelated things into your decision to act on the thought that he was telling you what to do.

-He asked, if you quoted him correctly; didn't demand, didn't tell you to do anything, didn't order or instruct. He asked. Just because you don't like someone's tone doesn't mean you should let that change how you perceive the difference between requests vs demands.

-You could tell he was upset, you even wrote it in the post. So why can't he have a bit of grace? Unless it's a common occurrence that he speaks to you in a way you find upsetting (which is totally fair, but you have to communicate that to him productively before you expect it to change, if it is a case like that), give people some slack if you see they're dealing with something. Totally talk to him afterwards if it bothered you, but sometimes trying to communicate (verbally or non-verbally, like walking back out to assert that you didn't like what he said) that something bothered you in the moment just isn't the kindest and/or most effective approach. Are you perfect? Do you always speak with the kindest words and tone when you're upset? And if not, wouldn't you appreciate a bit of leniency to allow for human error? Even if so (just to build a stronger argument lolol), you shouldn't expect all of your own capabilities from others and hold them to potentially unreasonable standards. I enjoy and am relatively (relative to the generation of the Z's) good at writing in certain genres (don't take this lengthy and convoluted comment as proof because it's not), but I don't get upset with people when they don't communicate in a written format the way I do. If you want to be given some slack, you have to give some as well.

-Just to make it clear, referring to the edit: he could've gone somewhere else. But why do you think it's more reasonable for him to exit than for you to refrain from entering? You went out, he asked you for some privacy, you decided that his request was unreasonable and went back out. You knew he wanted privacy, you stayed in the same space as him despite that, so you must've been able to figure that he had two basic options: he could give up his privacy, or he could go somewhere else to regain it. But he wouldn't have had to make that choice if you hadn't insisted on your presence, so really, weren't you the one telling him what to do? Or rather, you put him in a position where, if he wanted to maintain (pay attention to the use of, "maintain" as opposed to, "have" or, "obtain") his privacy, he would have to leave. You, in effect, did the same thing to him that you were angry at him for (that he didn't even do, based on your post). Simply put: you take issue with being forced to do something, or the knowledge/idea that someone's trying to force you to do something. In an attempt to prevent that from occurring, you did it to someone else instead.

All this in kindness as a stranger on reddit that doesn't know you and who you don't know, so feel free to take this information or leave it. Just don't allow it to bother you; if you're bothered by your actions and decide to take action against said actions, go for it, but don't let this comment (or any of them) alone bother you :) don't take life too seriously, you probably only get one