The problem w/ this is that Ze/Zir are supposed to be used when one has not yet been informed of a person's gender yet. This is too avoid "offending" them by assuming their gender. But, if somebody did NOT assume my gender, and called me by Ze/Zir I would be offended. I'd be offended that they second guessed whether or not I was a He/Him.
This is commonplace for the vast vast majority of the world. In order to use Ze/Zir without it devolving into a discussion cesspool, the practice of asking "what is your gender" needs to first be a general and "safe" social practice. But it just isn't. Asking somebody you've just met "What is your Gender" is not social taboo...nor could it ever be, as the world is too large and vast to start replacing the commonplace greeting of "Hi, my name is ___, what is your name?"
If a stranger walked up to you and said "Hi, my name is Susan, and I am a They. What is your name & gender?" wouldn't that make you uncomfortable. How would you react? It is just an awkward way to start a conversation.
This is why more legitimate Trans or Non-Binary people, and not just young progressive twitter users trying to be fashionable, do NOT get offended by people who assume their gender. It is to be expected, and unavoidable - as they themselves will assume other peoples gender for the sake of avoiding the awkward situation I described above. They simply (if they feel the need) politely correct the person, inform them of their prefered pronouns, and then continue the discussion.
It's not a big deal to them. What is a big deal is when somebody refuses to acknowledge them by their preferred pronouns on purpose, or harass/discriminate them as a result of their prefered pronouns.
I live in San Francisco, just blocks away from the Castro District. This district has more trans and non-binary people than anywhere else in the world. I've been politely corrected a few times...it happens, and they don't throw hissy fits. They understand. Twitter is not representative of the real world, and this Cartoon Network stuff is just a poor attempt of virtue signalling. The actual Trans Community doesn't even advocate the use of Ze/Zir for the same reasons I listed above. There is no acceptable social interaction where using such pronoun would be commonplace.
Very well put
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There is no good. There is no evil. There just is.