'The imagination is to try and understand why someone might not. But hey, you know what you would do in a hypothetical situation, so anyone who doesn't is automatically a cunt, right? '
IMO, yep, spot on. Cannot imagine any situation in which I would not offer shelter to my child and grandchildren if I knew they had no power or heat in this.
'And you feel qualified to tell other people what is wrong with them?
Yes, I do feel qualified to come to the opinion that such a person indeed has something wrong with them, they have twat syndrome.
'Get a hold of yourself and realise you are not the big I am.'
If it means I'm the big I am to have compassion and decency enough to offer my own child and grandchildren shelter in a blizzard when they are without power or heat, hey, thank you! I take that as a compliment 
'I would have offered you an extra heater. And offered to have the DC;s. Wouldn't have wanted all four of you staying in a two bedroomed house.'
Hard to run a heater when you have no power
? But hey, you'd see your own daughter with no heat or power in a blizzard because it cramps your style for a bit, says more about you than her.