A confused metaphor in 'Hancock'

Today I saw the film 'Hancock', which is about a tramp with superpowers who everybody hates, until he saves the life of a friendly public relations agent who helps to improve his image. At first I thought this was a straight piece of US propaganda: the hated superhero is a metaphor for the US army which wants to help yet is misunderstood and demonised by ungrateful liberals. Yet the plot complicates when this superheroes’ forgotten (amnesia) lover is revealed, who also has superpowers. It is established that when they are together they loose their superpowers and become mortal. But disturbingly rather than the characters accepting that it is better to be weak but together in love than strong and lonely, the film concludes with him keeping his distance and maintaining cold contact over a mobile phone. What is this film trying to teach us exactly? That love makes us weak and vulnerable, so we should reject it? Maybe I’m over-analysing, but if I was script writer I would have rounded the whole thing off with a simple ditch-superpowers-and-live-together-happily-ever-after style conclusion. Such an ending may seem a little disneyish and clichéd, but at least it would be true to life and free of parallels with Nazi philosophy.