What could possibly be wrong in that? Well, for a start, empathy leads us up a whole lot of wrong moral paths if we follow it blindly. You see a little girl crying because she has dropped the change she was carrying home to her mother down the drain; your heart goes out to her, and you pull a note out of your wallet and press it into her hand, telling her, "there, there, no one need know you lost it". Your action is spontaneous and totally selfless; she's a stranger, she doesn't know your name, you're unlikely ever to meet her again. And you walk on, somewhat pleased with yourself, past the woman rattling a charity can in aid of the homeless and starving victims of another Asian typhoon.
We are wired up to respond to immediate suffering, not to statistics. We don't suffer half as much reading of hundreds or thousands of death in a newspaper, as we do when we see someone we know crying. Empathy is unwilled, immediate, and has nothing to do with making sound moral choices.
It also has nothing to do with the emotional impact of fiction. A recent long-running story-line in a UK TV soap concerned a married couple, in which the woman had a terminal illness and wished to end her life voluntarily; her husband opposed her, partly, we must suppose, because he loved her and wanted to keep her around as long as he could. Let's not question the rights or wrongs of the characters' choices - they're only fictional, after all; rather, let's look at the way the story was served up to the viewing public.
The actors went to town with their escalating facial agonies; medieval wailing widows could learn a thing or two about emotional excesses from these two; their performances were positively Biblical. And all of it was shown in close up. The result is obvious: viewers saw all the tears and chest-beating and felt enormous empathy, their mirror neurons lighting up like the Coca-Cola Christmas convoy. Tears were wept. Some viewers even offered to help!
What is wrong with this picture? What, apart from people wanting to help characters who don't even exist?
Well, from a fiction-writing viewpoint, just about everything. Empathy may be an effective way to keep TV audiences hooked to a show so that you can raise the price of advertising slots (which, lest we forget, is the function of soap operas), but let's take a look at what emotional response was elicited. Did the viewer who cried at the husband's desperate attempts to keep his wife alive actually feel his anguish? Did the viewer whose heart broke when he accepted the need to let his wife go feel his sadness? No, they did not; they simply felt moved - mechanically, manipulated - by the portrayals of anguish and sorrow, but they felt nothing - nothing at all - of what the characters might be supposed to be feeling.
This is the fundamental difference between fiction - good fiction, whether literary or cinematic - and life: fiction gives us, the audience, an opportunity to vicariously experience someone else's life from the inside, as if living it. The novel does this par excellence, but it is possible to do it too through drama - the awards given to great actors, such as Olivier, de Niro and Depp, or to great directors, like Polanski, were hard-won and richly deserved. They forego the cheap and easy use of crude expressions in favour of character development by means of layered motivation. For only when we can think as a character thinks can we feel as they feel. In the case of the soaps, it is doubtful even the actors felt real emotion. It's probably beyond their pay grade.
So, both as a writer and as a consumer of fiction, eschew sentimentality and seek instead to walk in strangers' shoes. Sentimentality is toxic to fiction because the empathy it evokes is utterly empty.