It has been said, two things to never discuss are religion and politics. Of course, I often discuss both so boo to that. heh
Religion is a very, very touchy subject because people take it incredibly seriously. As the book states, people identify themselves as Christian, Muslim or Jewish. This can be problematic, especially when one religion (or ethnic group) thinks it is better than the other. Thoughts of superiority lead to oppression, which leads to the atrocities which have occured to many peoples. The discussion of religion is wraught with many issues, because simply one of the fundamental tenets of a religion is that you believe the teachings of the religion, thus in general, refute teachings of other religions. Engaging in religious discussions often can be similar to trying to knock down a brick wall with you head, it does not budge and your head hurts. I realize this is not the intention of this chapter, but that was a thought I just had. Back to topics relating more to the text, people are offended because they feel that another religion (or theory or belief... or evolution vs creationism) is out to prove them wrong. This is in general true, but I think it is more important to understand that know one is right. I personally feel this is one of very few truly universal truths, no one is right absolutely. While certainly we have sprinkles of truth dusted in what we say, no one knows or understands absolutely. The idea that anyone knows the truth to anything refutes the neccessity of dialogue (a concept J. S. Mill would certainly support).
Honestly, I think religious zealots need to come off themselves and understand that their beliefs do not hold true for everyone. While I have no problem if they want their children to be taught creationism over evolution, I cannot justify enforcing its inclusion in schools, when the majority of the scientific community disagrees with the theory. If you are teaching science, teach science. If you are teaching religious doctrine, teach religious doctrine. There is no particular reason why these two different subjects should be taught in the same classroom.
Now, conversely it can be and is argued that evolution does not hold true for everyone. Fair enough. As I stated previously though, the majority does rule in the end and while it may seem unfair that the minority must participate according the majorities rules that is generally how society has worked. Is that ethical? Maybe not, but in order to appease a few you must step on others on the way. From a consequentialist standpoint, that would not be particularly ethical. From Mill's standpoint, all ideas are valid and at least worthy to be discussed and considered.
I think this is where we run into the issue. Ethically, we have to teach the history and beliefs of every culture involved, yet we do not have the time or resources to do so. Thus, we run into the issue where the thoughts and beliefs of the many outnumber and outweigh those of the few.