>This fence has been compared with the Berlin Wall, but the wall was built to keep people in, and the fence dividing Palestinians from Israelis is designed to keep homicidal bombers out. In order to >protect >itself from illegal Mexican immigrants, the US built a fence on its southern border. Surely it's valid to question what is the difference?

The difference is glaringly obvious to the world, America has built a southern fence on its border, therefore the fence does not infringe onto Mexican territory. The apartheid wall that Israel has built illegally runs through Palestinian occupied territory, the very land which forms the basis of a future Palestinian state. So in all, most people are not against the wall itself, but against the fact that it encroaches on another peoples territory, cutting off villages from each other and deliberately stifling future land hand-over to the Palestinians.