I don’t think he denies that transgender people exist, but he does frame it as (possibly, but not certainly) a mental illness. He says that in his daily life he uses their preferred pronouns when engaging with transgender people.
He feels like there should be a more frank discussion about how transgender people fit into society, but frank discussions get shut down in today’s hypersensitive culture.
We can’t be so blindly “woke” that we ignore the very real physiological differences between men and women. A trans woman fighting in the UFC against biological women would be disastrous. Denying reality is not helpful to anyone. And the example I gave actually happened, Google Fallon Fox for more information.