It's the subliminal associations of this image that make me uncomfortable. When I first saw the picture, which sets an innocent domestic scene against the backdrop of a wall surmounted by barbed wire, it made me think immediately of The Boy In The Striped Pyjamas, John Boyne's novel about a young boy who is unaware of his father's work as the commandant of a Nazi concentration camp. The depiction of the two children, with their blond hair, Aryan looks and Thirties-style clothing, only reinforced this parallel, making me think the resonance was deliberate.
So rather than being a legitimate critique of Israel's military tactics in Gaza, I think Bell's cartoon allies itself with the distasteful - and yes, antisemitic - comparisons made by some critics between the actions of the Jewish state and the Nazi Holocaust. Or is it just me...
(Update: As Kellie points out in the comments below, and as I should have known, the cartoon explicitly references a WWI propaganda image, so maybe it was 'just me'...But deliberate or not, those other resonances were certainly there for me, and may have been for others, at however subliminal a level...)
Here's a short video by way of a response: