So why don't most people extend the same sympathy they would give Brits who don't like pictures of salmon, to Muslims who don't like pictures of Mohammed?

1. Because people who take their religion and its taboos seriously are low status in the West.

2. Mind projection fallacy: We assume most Muslims don't take their religion seriously like most Christians or Jews don't. We see them using a technicality to claim offence where there is none in order to control us or display dominance over our tribe.

3. They aren't part of our tribe. And worse they belong to a culturally powerful, demographically ascendant and politically threatening tribe.

Another thing I find interesting is that such a argument would never be set up using the example of piss Christ or a desecrated Talmud. I think the reason such a argument is employed using the Muslims as an example is because we quietly accept that Christians, Hindus, Shintoist and Jews are very unlikely to retaliate with violence compared to Muslims. We hide this so it seems that we are arguing about general principles but we are actually arguing about this specific situation based on appeal to consequences.

Note: I don't think this is the case with this LW article but I do think it is the case with many other ones available in the media and on-line.

PS: Excellent article! The debate it provoked is very much intriguing. Upvoted.