I didn't see the press conference. I wouldn't be surprised if those guys masturbated at all meetings.
But you had to have considered that in their own arrogance, they think they are well in the right in their actions. That within a large Western culture in this modern era (they are not publishing in Egypt), the freedom of speech trumps any perceived slight that might seem unreasonable or out of touch with modernity. Not that I agree with them, but you have to imagine that anyone telling them that drawing cartoons can be so hurtful -- especially when it's their visual language since they were children and that they aren't exactly rendering Muhammad as an evil villain or a fool -- is outright wrong and needs to "modernize" and conform to their perspective.
I'm sure those guys are still mind-fucked that anything seemingly as innocent as rendering a real, historical figure in a cartoon -- even if in a positive light -- could be so incendiary for some people. Backing down from that instinct of drawing-as-an-innocent-act would be incongruous with their beliefs. To them, they probably cannot envision a pluralistic society where reactions like that are considered reasonable -- any more than many Muslim societies today think that women's rights, gays who aren't killed for being who they are, or atheists are reasonable.