I think the idea that we shouldn't use Our Father because some people have negative experiences of fathers IS problematic. It's a different argument to the (age old) one about why God is seen as male. It's about whether we should be free to acknowledge the positive way most people love their fathers and use that as an allegory to the way Christians feel about God, or whether that's not allowed because not everyone has that positive feeling towards their father. But if you take that argument to its logical conclusion you'd censor out all mention of love between anyone, no mentioning of mothers (who might also harm some children), friends (who can also be cruel), etc.
We should be allowed to celebrate the strength of what for most people are positive and important relationships (eg with our fathers) without worrying about whether someone else might be offended. That's what's new about what he's said - it's about this modern hypersensitivity to offending people rather than correcting centuries of sexism in Christianity.