They have not forgotten that the white Southern churches were not on their side fifty years ago. They have not forgotten that none of the religious leadership of the white Bible belt ever saw any problem with lynching.
I think that probably explains a lot.
That is ancient history, and to a large extent applied to Democrats, not Republicans. None of that is true today as regards the religious right. It's message is values and protection from liberal values being forced down their throats by the government. There are no racial concerns, and principled objection to affirmative action in favor of a color-blind society is not racist in any reasonable, objective sense of the term. And if you want to look at ancient history, which party faught the civil war and freed the slaves? Which party passed the civil war constitutional amendments outlawing slavery and allowing for citizenship and voting rights? Which party was most resistant to civil rights acts in either 19th or 20th Century? Which party did most members of Southern white churches and lyncher mobs belong to? Which party has a former KKK member in the Senate? It was NOT the Republican Party.