Look at these images.
http://www.geographic.org/maps/new1/gaza_strip_maps.html
Hamas could have dug in in the large unpopulated areas shown, evacuated civilians from around their positions in built up areas, or just concealed themselves.
They chose to fight surrounded by civilians.
That is a war crime.

There are very strong grounds for thinking it was in fact used as an anti-personnel weapon in Gaza.
What are these very strong grounds please?