Regarding the translation of Genesis 12:2:
It is true, as one astute observer pointed out in the comments, that the second verb (to be a blessing) is an imperative. But there’s a reason our English translations, including the ESV, KJV, NKJV, NASB, NIV, TNIV, NLT, RSV, NRSV, all say “you shall be a blessing” or “so that you shall be a blessing” or something similar. Victor P. Hamilton explains:
Hebrew grammar provides numerous instances of an imperative (with waw- copulative) depending on an earlier imperative. Here the first imperative states the exhortation, and the second imperative touches on the results which are brought about by the implementation of the first imperative [e.g., Gen. 17:1; 1 Kings 22:6; 2 Kings 5:13; Isa. 36:16]. Applied to Gen. 12:1-2, this construction means that the first imperative, go, is related as effect to cause to this second imperative, be. Abram cannot be a blessing if he stays in Haran. But if he leaves, then a blessing he will be. (The Book of Genesis, NICOT, 373)
In other words, Hebrew grammar strongly suggests that the second imperative should be translated as a result clause not a command. And this is how our English translations uniformly render the verse.
But the refutation of McNeal’s treatment of Genesis 12 does not rest on grammar alone. The entire story of the patriarchs demonstrates that God is the one blessing apart from any blessing strategy on the part of Abraham. After Genesis 12, the narrative follows different individuals and nations which prove the promise of God that whoever blesses Abraham is blessed and whoever curses him is cursed. God blesses Abraham’s family despite themselves and he blesses those who bless Abraham. But Abraham never takes his call as a commission to go think of ways he can bless the nations around him. This doesn’t mean we shouldn’t be kind to others or seek the good of our cities. We should. But the call of Abram is not about a community blessing program. It’s about God’s unilateral promise to bless the fumbling Abraham and bless the nations through faith in the promised Seed that will come from his family tree.