Term for “powerful, moving words”

What is a term for powerful, moving words? Rhetoric implies the opposite (“empty” rhetoric).

The nominee’s speech was filled with XXX

Rhetoric most certainly does not imply the opposite of "powerful, moving words"! What implies the opposite, as you yourself note, is the adjective "empty" attached to it.

As the New Oxford American Dictionary defines it:

rhetoric the art of effective or persuasive speaking or writing, esp. the use of figures of speech and other compositional techniques.

Note the words "effective" and "persuasive" in that definition. You have to add negative adjectives to the term to make it bad.

As Farnsworth says in the preface to his Classical English Rhetoric:

Rhetoric is a vast, old, and honorable discipline. It may be defined most broadly and simply as the use of language to persuade or otherwise affect an audience. ... It is certainly possible to write well without rhetorical figures, but most of the best writers and speakers — the ones whose work has stood up the longest — have made important use of them, and figures tend to show up often in utterances that are long remembered.

So I would suggest not only that your premise is wrong, but that the term for powerful, moving words is, in fact, rhetoric. If the word still bothers you, add a positive modifier to it.

The nominee's speech was filled with powerful rhetoric.

Emotive? Wouldn't suit every occasion but often has the meaning required.

Lively or vivid to emphasize the more positive aspects of powerful words?

"Demagoguery" could apply, perhaps?