I've seen this posted before, with references to racism. Islam isn't a race, it's a belief, and should be treated as such.
Making fun of something that can't be helped, like race, gender, sexuality or disability is not OK, in my opinion. But if we can't make fun of a belief, just because it might be offensive, well. I wouldn't want to live in a society like that.
Should we not be allowed to make fun of politicians, because they find it offensive? Conspiracy theorists? Racists? Who are we allowed to offend? Why should religion be special?
A person has every right to their view, and to express that view (as long as others aren't put in danger). But equally, others have the right to think that their view is stupid, and express that opinion. If the Muslim soc decided to wear t-shirts making fun of atheists, then I wouldn't be happy. But I would respect their right to do so.