Not defending anybody but a lot of labels are thrown around here like kidnapping vs. taking prisoners of war - what is the difference in wartime?
A central grievance of these organizations is the need to exchange prisoners of war to attain peace. The Palestinians and pro Jihad Islamists will keep taking political prisonors like this until some of the 9000 + prisoners of war kept by Isreal are exchanged or even addressed publically.
They want to make an equitable exchange since the value of human life should be considered equal regardless of race or religion. Again I don't defend them or either side for that matter. But from a humanitarian standpoint both sides are taking prisoners and one of the sides is hiding it and not allowing mass media to broadcast the facts.
Some background:
http://www.hrw.org/backgrounder/mena/isr0622-back.htm