To be truthful there are not many "Amusing religious cartoons" any more as they have gone the way of Irish and Polish jokes under the weight of political correctness, otherwise known as actions likley to incite religious hatred..
That only applies to jokes about Muslims. Hindus and Buddhists never did seem to be particularly joke-prone; whilst Christians - especially pastors - are quite happy to tell jokes at their own expense. The reason this particular one was deemed funny was because the artist is American and its an American site. I suppose I also found it humorous because I've never seen a visual representation of it. Its only ever been a verbal joke.
Fair enough.
However I would dispute your point about it only being Muslims who get offended.
I did a charity gig about a year ago and was sent a list of "subjects not considered suitable targets for humour". This included, among other things - Ethnicity, disabilities, sexual orientation, religion (any and all), obesity, anorexia, mental illness (where not covered by disability), poverty, unemployment.
The final line of the letter stated that in order to avoid giving offence comedy should, if possible, be restricted to the weather and politicians.