Of course trans ideologists don't accept that your body and sex are one and the same and therein lies the madness
Eastern religions do not believe that body and soul are one and the same. Hinduism, Buddhism and other religions in India and further east see the body as a mere vessel, a thing we live in, and not what we are; to be honoured and kept healthy (see Yoga for example) but not who we are. And |Hindus and Buddhists are not mad or stupid by any means.
Both Hindus and Buddhists believe in reincarnation, that is, the spirit moves on to a different body to reap the karma or resolve issues from the last life, growing in insight until final liberation, or moksha, or samadhi.
This would actually explain why small children might declare I AM a girl/boy with such force. Hindus or Buddhist would say it is a residual memory, a latent impression in the mind derived from the last life, in which they were that sex.
BUT and it's a strong but its the present, and the present life, that counts; memories of the past have to be forgotten, the individual soul (or whatever you want to call it) needs to move on by accepting the conditions in THIS life and learning the lessons of THIS life.
To insist on upholding residual traits of a past life, to cling to a former sexual identity, would in both these religions mean you have burdened yourself enormously and cannot grow, and added even more karmic debt to your --- soul or whatever. It's the worst thing you can do. You are supposed to learn new lessons, and the "new sex" would be part of that, even if it feels strange at first. The memory would fade after a while.
Neither of these religions believe in gender as an identity or as a reality.
I know that such "theories" might sound ridiculous to rationalists but I've heard the reincarnation argument being offered by transpeople before. It's utter nonsense to offer that as an argument for the transing of children, so if you ever hear that argument -- there's your counterargument.