I would definitely agree that it is not always the case. If you have restated your idea twenty different ways and someone still does not understand the idea itself (regardless of whether they agree with it or not), the problem may exist elsewhere.

As a rule (subject to any of those generalization problems), though, I think it is fair to say that step one is to presume initially (for the benefit of the conversation, if not for utter honesty) that the problem is on your end.

Looking back on what I just wrote, I wonder why people say I'm too verbose ...