It's hard for us, living in a heavily secular and advanced (relatively speaking) society, to understand and accept that there are many people out there who truly believe in their religion to the point that they will kill you and themselves for it.
I don't know why, perhaps it's a result of cultural 'brainwashing', but we always hear from large sections of society, even from the non-religious amongst us, that religion makes some people do good, however, these same people will invariably completely deny that the opposite is also the case- that religion makes some people do bad. It's stupid and needs to stop. Either claim both or deny both.