They don't live a normal life. They live a life at odds with nature and biology, with an exponentially higher chance of killing themselves.
If your kids climb up on the roof and want to pretend to be Superman you wouldn't be accepting of it, because it's false and dangerous. This is the same thing.
The only thing that is even open for debate regarding biology and nature is their hormones and genitalia. Everything else that people actually concern themselves with is societal. Biology doesn’t inform which bathrooms are used or who competes in which sporting events. We created all of those things, and assigned who does what or goes where based on societal norms. Saying a trans person shouldn’t be allowed to do something because of science is misleading.