Flippin' 'eck! OK, Cameron is a Tory, and as such a blithering idiot - we know this. But 'as a father of daughters', what he has seen is his girls getting excited, talking about it, avidly following the matches and so on. His youngest girl is 13 or so, so there wouldn't have been much jumping about, but as a Dad and Granddad I know that having excited youngsters around can be a robust (and occasionally painful) experience.
The key word here is experience. Anyone can have empathy, of course they can. I can feel empathy for the plight of LGBTQ+ people even though I don't share their specific sexuality etc. But I cannot share their experiences, only they know the full impact of what they go through. The experience of anything naturally changes your viewpoint toward it, and in many cases, that is what is meant by "as a parent". Which is why the statement is irrelevant in some matters but very much so in others.