I hate to be called a liar. I go to great lengths to try to make what people understand of what I say to be true. As such a person, it's been said to me many times, and I think it applies here, "If you're so confident that what you're saying is true, then there's no harm in proving it." It takes only a moment to tell somebody where you learned something, and if your sources are sound, you should be proud to lead them directly to it. It has been said here, or at least it's how I understood it, that if your sources are too precise, it can serve to take facts out of context. Well, yeah, they can. But they can also serve to give us a better understanding of what exactly the context is. A 500 page book may be too much context for most small pieces of information. Even a 50 page book may be too much. If you give me the page number, I can choose how much "context" I want to read about. To be friendly, you can give the page number, and then say that you strongly recommend that you read the context. Actually, I think all this is just "how to behave in social situations." If it doesn't matter to you that some people may think you're a liar, then you really have no motive to back up what you say. That's my personal view on this anyway.
Maybe that isn't an exact quote up there, but I think the meaning is still there. Somebody feel free to correct me if I'm wrong.