I don't think Ralph Miliband hated Britain. From what I can gather from what's been written about the man's life, he only disliked the way the establishment works in this country, and wished for a system that affords opportunity for all, not just those from privileged backgrounds.
He might have had a few dodgy communist beliefs, but it was/is his absolute right in this country to hold whatever beliefs he liked. When the Daily Mail says he hated Britain, they mean he hated their exclusive and elitist vision of Britain – which represents a very small minority.
So who really hates Britain? The DM is no friend of people such as me. It's no friend of anybody in the area where I live. It regularly slanders and attempts to demonise every demographic of people who make up my local community. When the DM refers to Britain, it's only talking about a small percentage of the population of this isle. It's not talking about people like me, or my neighbours, who Ralph Miliband wanted a fairer deal for, and who the DM wouldn't piss on if on fire.
If you see Britain in a way that is inclusive of all of the people who live here, and not just the elite toffs, then there's a much better case to be made for saying that the Daily Mail hates Britain, than for claiming that Ralph Miliband ever did.