How do you explain Winston's feelings of respect, even love for O'brien?

There is a twisted "bromance" going on here. Winston respects O'Brien's quiet manner and keen intellect. O'Brien finds the same in Winston. This is why O'Brien has been studying Winston for so long instead of just vaporizing him. Even when Winston is being tortures, he loves O'Brien. O'Brien becomes the only person who can stop the pain: O'brien is Winston's saviour, his refuge.