That Loki is "non-binary" is an irrelevant detail and makes all the sense according to his myth, there is no problem with it and I have not seen practically anyone who has a problem with it itself.
But as always, the problem is all the shit that is created around it.
The attitude of the media, the activists, the company, etc. It is the repetition of the same old shit, ignoring the entire cultural context or the situation to accuse whoever says something of being some -ism.
People do not mind that Loki is "non-binary", it bothers them that such a dumb detail has become the absolute center and practically the only relevant detail of the character and the series.
I swear I still don't know what the hell the series is about because the whole last week I haven't seen any article about it other than "Loki is non-binary."
I see it every day, at any hour, in all the media. Plot, characters, development, background? what is that? Loki is non-binary, did we already say that Loki is non-binary?
It is, as always, the reduction of the characters to their identity, their innate born characteristics that should be irrelevant but in the current era surpass any other characteristic.
Another thing that annoys ppl is the use of this by activists to try to validate their shitty theories. Loki is "non-binary" because he is a God with MAGIC powers to shapeshift, and like all shapeshifting Gods, he fucks anything (Zeuuus).
That introduces "non-binarism" as a fictitious concept because if he changes shape, he can invent a new sex or adopt forms of animals or aliens or anything outside the human spectrum, so he would indeed be "non binary".
If you think that a FICTIONAL character with MAGIC powers that allow him to mutate in ways completely impossible in reality validates your ideology in said reality where that is impossible, you're not right in the head. It's like to say that ghosts exist because of The 6th Sense.
What people are facepalming about is not a Shapeshifting god being "non binary", it's at all the fucking circus arround it from media and activists. A combination of the company presenting that as the relevant thing, that it seems the only thing the media and activists can see, or that it's used to validate modern concepts from a specific ideology that are HIGHLY contested in the scientific field.
Wokes of course willfuly ignore all of this to just claim "homophobes are angry Loki is non binary" because it's the default tactic to avoid criticism