OP said Muslims are very easily offended. You responded that studies show people take offense when you challenge their political or religious beliefs. This is a non sequitur. The fact that people (in general) take offense does not in any way disprove OP's contention, which is that Muslims (in particular) are verily easily offended.
You follow this non sequitur with a false equivalence: the same is true of atheists or people with strong political beliefs. This is obviously, objectively untrue. Speaking generally, Muslims take a much greater degree of offense to comparatively minor challenges to their beliefs.
Consider the example of sacrilegious art. 'Piss Christ' (a crucifix submerged in the artist's urine) has been exhibited for 25 years with the occasional vandalism attempt. Compare that to Islam. Dutch director Theo van Gogh was assassinated 2 months and 4 days after producing a short film criticizing the treatment of women in Islam. Novelist Salman Rushdie has been under police protection for 30 years because a fatwa calling for his assassination was issued after he wrote a novel that could be characterized as mildly irreverent toward Islam (much, much milder than Kevin Smith's 'Dogma' was toward Christianity, for example).
The publication of the book and the fatwā sparked violence around the world, with bookstores firebombed. Muslim communities in several nations in the West held public rallies, burning copies of the book. Several people associated with translating or publishing the book were attacked, seriously injured, and even killed.[note 1] Many more people died in riots in some countries.
Charlie Hebdo mocked Christianity and Judaism for decades. Yet only Muslims took such offense that they felt the need to kill 12 people. An event featuring cartoon images of Muhammad in Garland, TX was attacked by Islamic gunmen the same day it opened. The BBC, no stranger to jokes about Christianity, is too afraid of Muslims to joke about Islam.
And it isn't just 'sacrilegious' art. Women, even non-Muslim Western women living in the West, have been severely beaten for offending Muslims by wearing shorts in public. A Western couple (again, living in the West) were brutally beaten because they offended Muslims by eating ham toppings on their own pizza while minding their own business.
As a group, Muslims are much more likely than the general population or almost any similarly-sized group to take extreme offense over comparatively minor grievances and respond with extreme violence (1% of the US population and responsible for half the deaths from extremist attacks).