I would say your comparing two different things... the case you posted about a Buddhist is one person, of a certain faith, raping a girl. He is not raping the girl and citing buddhist beliefs as the justification for doing it. Your not going to be able to find a buddhist belief that can be twisted into "its ok to rape a girl" and your probably not going to be able to easily 'spin' any reference in the Bible, unless you just completely make up a belief that doesn't exist. ISIS and other organizations that stem off from the Islam religion seem to quote specific and detailed references in the Qu'ran which gives them the 'feeling' that they have a God, prophet, or whatever behind their actions.
I am comparing a RAPE with a RAPE. The reasons may be different but I don't care why did the person commit this crime but the only thing that matters is that he committed the crime. He may quote many reasons but that does not make his crime meaningless. A criminal always thinks what he has done is right and quotes a religion or another reason for his crime and then people start debating on it. This indirectly SUPPORTS the crime saying that here religion is at fault and NOT the criminal as he committed the crime because his religion tells it is right. Does this mean that all people who belong to that religion should commit such a crime? Why not blame him instead of the religion?
I agree that some beliefs are wrong but it's finally the person who commits a crime and not all people who belong to that religion commit such crimes.
In other cases, people blame movies/alcohol/the girl's character and say that their crime is justified. It's wrong as the criminal committed the crime because he WANTED to commit the crime. Here as well those criminals wanted to assault that girl and hence they did it no matter what they believed in.