Reading through this thread is really sad - so many judgemental people out there. I think some are aimed at me as I was the first person to post about my little girl saying she is a therian.
First of all, like a PP said, you don't know which parents are 'encouraging' it or not behind closed doors. There might be things going on in the background like autism, but really no parents are going to be actively encouraging their kids to believe they're actually an animal not a human are they?
In my case, my 7 year old has always adored animals and has pretended to be them since the moment she could talk. She is not autistic as far as I am aware (although it runs strongly in one side of family but I have no concerns).
She doesn't have a phone or social media, and doesn't have access to the Internet (other than with direct supervision anyway). She is occasionally allowed to watch YouTube kids. However, she does attend school and these things trickle down. I think she heard the word therian from her step sister on her dad's side and again from kids at school. There are a few different groups in different years who call themselves therians, I've seen them dressing up outside of school as my daughter does, and they talk about it at school. They are primary aged and its completely harmless and I'd say normal!
To them, the word is not sexualised and simply refers to believing you used to be an animal in a past life and still have some of the traits. I think it is a bit of a fad or a trend at the moment and more than likely will pass.
OBVIOUSLY if this carries on into secondary school or older it may be more of a problem, but I would certainly not ever let her wear a tail to school or demand a litter tray or any of these stories you hear.
But what I am not going to do is shame my 7 year old for pretending to be a cat. I don't encourage it and certainly don't encourage some of the language she's learnt around it, but I truly think the bigger deal I make about it the more she may be pushed towards rebelling in the future.
Her and her friends are not hurting anyone, it's not sexualised in any way shape or form and are just having fun. I will continue to reassess how I deal with it if it carries on when she's much older.
People need to be less judgemental and much, much kinder.