The Israeli security wall doesn't do very much to protect the people of Israel. In reality, this wall is like the border fence between the United States and Mexico. Fences don't keep anyone out, and they're easy enough to dismantle or breach. Therefore, Israel should focus upon fortifying its borders with increased security measures aside from the fence.
The wall should not be dismantled because it does improve security. Although it may not be the most effective forms of security for Israel, it does help to some extent. It helps keep people who would cause violence from getting into the country. It helps make it harder for violence to happen.