It's one of the biggest problems in this world. We have to elucidate the science of it. I have a vague idea: the avegare skin resistance of men is considerably higher than that of women. This seems to be related with the "ability" o fmen, to shut their mirror neurons down, which means that they do not develop compassion in that moment (which his conveyed by the mirror neurons). You have to find a way to open the mirror neurons. I can only think of two ways: one is "scientific" - there seem to be indications that strong magnetic fields influence the mirror neurons. So my suggestion: let them see what they did to others in a strong magnetic field (of course, expert psychologists would have to do this experiment) (it is, of course, srongly advisable, to open their "resources" first, in other words make them remember a situation where they were really loved or appreciated by somebody). If they do not agree to any psychotherapy at all (a really good psychotherapist - but they are very rare! -can also open the mirror neurons), there remains only the "hammer" way: you do to them what they did to others, but with telling them that you do it so that see and understand what they did. But this requires enormous patience and intuition, since they will run away, if you overdo it.
