I don't think you have a real understanding of terror related topics as it applies to Israel. In an area of the world where getting ak47's is easy as heck - you can go a few countries away from Israel and buy them at open air markets - it makes a lot of sense to make sure no one is carrying guns and other weapons made with heavy metals into your airport.

The security is made of layers - just because they are checking for heavy metals doesn't mean that they don't know anything about (or are ignoring) plastic explosives or ceramic guns.