During Sunday's Jerusalem Day events, a Palestinian boy, perhaps 10 years old, was chased down an East Jerusalem street by a very angry officer of the Border Police. The boy tripped and fell, then picked himself up just as the Border Police officer reached him and tried to grab him. But a 22 year-old female Israeli activist prevented the boy's arrest by throwing herself between the two, allowing the Palestinian boy to flee. Jerusalem Day is meant to be a celebration of the city's 'reunification' following Israel's victory in the 1967 war. In practice, it is a day for Israeli…