I think people can experience A, B, and C, he's saying "I was like A, but I learned to be like B, therefore A does not really exist". It's a bad argument. It's like claiming that, because you have dyslexia and learned to read, dyslexia doesn't exist, even though other people who are dyslexic can have a severity where they can't learn to read.
He desribed his own experience of learninig to visualise. That is entirely valid thing to say in the context of "is it learnable or unchangeable or something in between".
He was neither rude nor dismissive. You was dismissive.
Also, dyslectic can learn to read. They have difficulty with it, including in later age. But "cant learn to read" is not that thing.
He rejected the idea of it being fixed for anyone else, based on it being changed for himself, which is uncharitable at best. Some people with dyslexia are incapable of learning to read, maybe you should check it out. That doesn't mean every dyslexic is incapable, but that's a real variation. And you're rejecting the idea of that yourself, which also feels pretty uncharitable.
