Who or what will I hate?

I really don't get these people who often quote "Don't hate the religion, hate the people behind the religion."

Now, let see.

Suppose there's this religion who teaches violence as the way to salvation. That they must kill all those who doesn't believe their doctrines and that they must make this religion the only religion on this planet because this is what the one true god commands them to do. So whose fault is that, the people who believed this religion or the religion itself?