I'm not sure how you think dictionaries work.
Well, let's talk about that, then.
Here's how I think dictionaries work. They record the common meanings of words. They are useful because sometimes we see an unfamiliar word, or a familiar word used in an unfamiliar way, and we can try to deduce the intended meaning of that word by looking in a dictionary.
If we are arguing, for instance, whether the word "alien" is always a negative term or whether sometimes it is used in a neutral manner, then looking in a dictionary is appropriate.
If we are arguing over what one of us actually meant when using the word "alien", then the dictionary is not so useful. The person who used the word is the authority here, although a dictionary can help him understand that, whatever his intentions, he misused the term.
And yes, in a perfect world where spherical cows fall in a vacuum, that should end the subject. But we're in the real world here, and words can discriminate and marginalise. Words wound. I once had a friend, until I said something dumb and offensive because I was being stupid at the time, and now she will have nothing to do with me. My words wounded her, and no amount of apology or explaining "what I really meant was..." is going to fix that.
Take a piece of paper. Crumple it up into a ball. Then flatten it out again. Can you see the creases? The wounds caused by words are like that.
We are going quite afield from the issue at hand, which is the appropriateness of the use of "alien" to describe non-citizens, not the issues you had with your friend. It is a meaning that, far as I understand it, is used legally. It is synonymous with "non-citizen".
Now, don't get me wrong. If I think that large numbers of persons do not know the literal meaning I intend, and that they will take offense at "alien", then the word "non-citizen" may be prudent, cumbersome as it is. But, the person who takes offense at my use of the word "alien" and who
retains that offense despite a clear explanation of the relevant meaning is the one at fault in any dispute. Of course, it can be better to avoid dispute, but this does not change the situation.
I disagree, and have explained at length, that the word "alien" does not include any negative connotations.
In fact, you haven't. You've blathered[1] about "othering" and were once pressed to look at the dictionary, where you carefully pointed out various definitions that were not the relevant definition, and you missed the ones that mattered. You did not explain at length why your willingness to take the term as insulting is reason to believe that it is insulting.
Immigration attorneys use the term "alien". You know that, right? They have to, because the law uses the term[2]. Are they insulting their clients? Or are they using a term-of-art that has no negative meaning?
I can see that, yes. But that's not my fault. I'm just stating facts -
you are the one who's interpreting them wrongly. How is that my fault?
I suppose you think that's clever, but I don't see it. I have discussed carefully explaining one's meaning when there is disagreement. You are pretending that I've said the speaker is always right or something.
But, so long as you use a juvenile smiley face rolling his eyes, you may well pretend to have the upper hand. Kudos, you clever person, you!
[1] Just to be clear, yes, I know this is pejorative. In fact, I intentionally claim that your so-called explanations are obviously lacking any reason.
[2] If I'm mistaken here, someone can correct me.