G-d said to Moses, "Observe! I have made you a master over Pharaoh, and Aaron, your brother, will be your speaker.
You shall repeat before Pharaoh everything I command you, your brother Aaron shall speak it to Pharaoh, so that he send forth the Israelites from his land.
Shemot 7:1, 2
At this point in the narrative, Pharaoh, the embodiment of evil in his day, was at the height of his power. No human power could resist him, only G-d Himself. This is why G-d told Moses, "Observe! I have made you a master [Elokim, literally, 'G-d'] over Pharaoh." He channeled His own Divine power through Moses.
This is why G-d told Moses to repeat verbatim-- in Hebrew!--what he heard from Him. The purpose of his pronouncements was to break the power of evil even while it was at its greatest power. Moses, as a human being, was not involved in this at all; he was simply the channel through which G-d's power could attack Pharaoh. Only after this power had been broken was there place for Aaron to speak to Pharaoh on a human level.
Moses was able to serve as a conduit for this Divine power for two reasons: first, because he was the Divinely-appointed leader of his generation, through whom G-d's blessing flows into the world in any case; and second, because Moses had already despaired of using his own gifts to accomplish his mission. Once he was void of all ego and pretension, he could serve as a transparent conduit for G-d's power.
Similarly, there are times in our own, personal lives when our inner "Pharaohs," i.e., our animal drives, seem to have the upper hand. At such times, the best way to overcome these drives is to channel our inner "Moses" and rage against them, insult them, and humiliate them. Exposing them for what they are breaks their power over us.
The same is true regarding our mission to oppose the forces of darkness in the world at large. In this effort, we are all emissaries of the leader, the "Moses" of our generation. Of course, we must always convey G-d's message in a pleasant and peaceful way, just as G-d commanded Moses to address Pharaoh respectfully. But at the same time, we must approach our "Pharaohs" fearlessly and forcefully. If we remain true to G-d's message that "Moses" communicates to us--just as Moses had to convey G-d's message to Pharaoh without embellishment--we can break the power of darkness and help bring G-d's redemptive light to the world.