Your fellow Muslim failed to understand so I will try it on you.
The problem here is that anything can be interpreted to be an insult. With religious beliefs, it is not as easily discerned as an 'F U'. Get it? Reza Aslan claimed that as a scholar, he has an obligation to question Jesus' virgin birth, of which it is a vital part of Christian theology. If we are as intolerant as the Muslims are, we would have beheaded him before he even have a chance to publish his blasphemy. Instead, we welcome Muslims' and atheists' scholarly or not so scholarly expositions on Jesus and we tolerate Serrano's crass insults.
And people have the nerve to look down on Americans. Look in the mirror and see the pathetic kind you are.