One can point out what God had to say by directing others to the Scripture He inspired. That does not constitute *speaking for God*.
Speaking for God would be telling you that Dancing is a sin. Or that you shouldn't go to movies.
Directing someone to the passages that say, *Do not murder* is not speaking for God. God has already spoken on it and put it in writing. The person pointing it out is not speaking FOR God.
Well, you do more than point, you interpret.