When you emphasize varying words in the same sentence you get varied meaning. Perhaps you've done this excercise below or played it as a party game.
Consider the sentence "The man went up the hill." Emphasize a different word in the sentence each time you speak it and a different meaning is conveyed each time.
- THE man went up the hill (designating an auspicious moment).
- The MAN went up the hill (as opposed to others who may have done so).
- The man WENT up the hill (identifying that it is a previous action).
- The man went UP the hill (differentiating from other things one might do on a hill, such as roll down it).
- The man went up THE hill (showing the importance of the place, especially in relation to other hills he might have gone up).
- The man went up the HILL (making sure you understand it was the hill he went up and not up the staircase or ladder).
Emphasize nothing in this sentence and you introduce vagaries of meaning. The listener cannot really know what you mean, even with a simple sentence, and that assumes you haven't already bored them to tears.
A choice to try to emphasize everything is impossible. It amounts to shouting. THE MAN WENT UP THE HILL! People tire of you and stop listening at all - no matter the importance your message it its accuracy -- if your only tone is "soapbox."
Differing emphases convey differing meaning, but they are not in contradiction. They are modulations rather than contrasts.
Effective communication requires such modulation. We do it all the time unconsiously. A person emphasizes within a message based upon what they believe the listener needs to hear or is listening for. And if they discover they are wrong, they shift (modulate) to emphasize something different until the connection is made and the listener demonstrates understanding.
Take something important to you: a moral code, a political persuasion, a marketing message, a religious conviction, an allegiance you hold dear, an expression of love, an instruction you wish to convey. In any such you have a message to give, something you are going to emphasize. You can't emphasize nothing and you can't emphasize everything and successfully communicate. You have to emphasize something and then be prepared to modulate the message.
There may be something you prefer to emphasize within your message because it is most important to you. You might feel you are compromising to emphasize something different within the message than what you prefer. You would be wrong to think so. Sure, you might want to always enter the front door of the message, but sometimes it is more effective to show it from the back, through a window, via flight overhead, or from its foundations. If you are unwilling to modulate you ensure the ineffectiveness of your communication, however consistent your message may be.
I think all this is a bit paradoxical -- emphasizing modulation. It is one of the many a leader must embrace.