Pls read my reply to brother Behroz Batliwalla .I hope you will have a clear about the discussion which I wanted to have under this heading only for the sake of improving my understanding of 4:3 .
About the situation which you quoted I can only say
7:28 (As an example) when people commit an indecency they say, "We found our forefathers doing it and God has enjoined it upon us." (Made it natural for us). Say (O Prophet), "God never enjoins indecency. Do you attribute to God that of which you have no knowledge?"