It's worth quoting what he actually said:
I know the word ‘father’ is problematic for those whose experience of earthly fathers has been destructive and abusive, and for all of us who have laboured rather too much from an oppressively patriarchal grip on life
And... he's right. If your experience of 'father' is abusive or violent, then that language is a barrier. It doesn't mean that that language is wrong or unbiblical, but simply that the images and languages we use for God are a barrier to some.
Fortunately the bible has plenty of other language and imagery for God. There's this from Matthew, for example:
how often I have longed to gather your children together, as a hen gathers her chicks under her wings
This is not new. Augustine wrote about God as a nursing mother, bringing milk in the form of Jesus to nourish us. So did St Anselm, who picked up on the hen gathering her chicks image, to talk about Jesus our loving mother. Calvin compared the pains of the crucifixion with the pains of labour. And one of my local saints - Julian of Norwich - talked about "God our loving father; God our loving mother..."
So, if he'd tried this 500 years ago he wouldn't have been burned. He would have been entirely in keeping with generations of religious thought.
Really, it's only in the last couple of hundred years or so that we have lost this language of motherhood and nursing from our understanding of God.
This is not about trans people or about gender neutral language. This is about the church recognising the barriers it chooses to use present, and calling on the wide range of metaphor and imagery it has both in the bible and in two millenia of religious thought to, in the words of Jesus, gather everyone in.