Deadliest religion ever?

[masterofpuppets]

If religion is used to justify violence, then it can be deadly.

I suppose you are correct in a way, but you could argue that it is the person committing the violent or terrorist act that is deadly not religious ideas themselves, no?

Religious ideas can lead to violent behaviour though. If you have faith in a god that rewards certain types of violence with eternal bliss, it is the religion itself that instills such sadistic attitudes into its followers. One can personally justify any action based on faith and utmost conviction, and that's a danger brought by religion itself.