As I said, they all reflect objective truths. They're descriptive. Mx is not.

Call me big master pimpin'. I will request you be fired if you do not

It has barely any history prior to 10 years ago. Just because some nobody said it once in the 1970's doesn't mean its been colloquially around for 50 years. The source of it "being around from the 1970's" is a dubious article written in 2015. https://www.telegraph.co.uk/men/the-filter/11597192/Whats-it-like-to-be-a-Mx.html

That's a name, not a title. You don't get to choose titles, they reflect objective truths.

Ms/Mrs/Mr all reflect objective truths. Mx reflects how the person feels.

Mr/Ms/Mrs all makes sense.

Mr -> You are a male

Ms -> You are a female

Mrs -> You are a married female

Mx -> You uhh feel like you are neither male or female or something. keyword being "feel". The 3 above all are objective characteristics. The latter is not.

An adult should be able to teach kids without feeling the need to impose their own wacky views on them. Just use mr or ms. You are an adult, you can handle it.

Freedom of speech does not mean freedom from consequences

You don't have free speech in a childrens class room.