they can make a difference, because they are the closest thing to direct communication (other than action) that we have. sometimes action takes things too far, and we need words to step about cautiously.
words, however, are labels packed with preconceptions that lead to misconceptions. for example, a friend of mine rejects the term "argue" unless voices are raised, when raised voices actually aren't required in argument. many people tend to assume that words mean certain things simply because of their first reactions to the words, without considering what the words actually mean.
i have come to think that certain word combinations in poetry can evoke certain moods through sounds, imagery, rhythm, tempo, etc., and in this way, poetry could succeed where language often fails in communication because of the poor users of vocabulary. but, this would require masterful manipulators of language, and only reach the people who read poetry AND take it seriously.
i think that if you can understand your words after putting them away for a week or so, someone else can, too. if someone understands your words, this person is affected by them somehow. you just have to engineer your words so that they affect others in the way and to the degree that you most like.
but, then again, i'm rambling, and i have no idea if this could actually be done. i hate words because they are misunderstood.