IMPUNITY - OR exemption from punishment - has been correctly called a culture, a way of doing things to which a particular community has become accustomed. It is almost inevitably mentioned as the primary reason why journalists and political activists continue to be killed in the Philippines, where a culture of impunity has indeed taken root. But it also applies with equal validity to the killing of nearly everyone else, especially the poor and powerless. Few murders in this country are ever really solved, with the perpetrators and masterminds being arrested, tried and punished.