Well, given that they could have run this petition *between* the publication of the offending cartoons and the killings but didn't, I can only assume that all 100,000 of them were, like myself, completely unaware of the existence of this magazine, until it was brought to everyone's attention (in UK) by the massacre.
What is the point of being offended this late after the event?
And what do they expect the British government to be able to do about a publication from France, in any case?