Why does 'Thou shalt have no other gods before me' directly oppose what happened at Babel?

Les explains that after Abram came out and was given the promises—the 'I wills' of chapters 12, 15, and 17—God brought things to the place where man has to understand what is right and what is wrong. Because man does not seem to get it, God gave the Law. He laid it down punctually and said, 'Thou shalt have no other gods before me.' Les says that right off the bat this flew in the face of everything that took place at Babel, because Babel was the beginning of all false worships. So God came right back and said, 'Thou shalt have no other gods before me,' and then continued through the rest of the commandments. Les also notes that very few people understand this. He connects it to Romans 3:19-20, where Paul writes that the Law speaks to those under the Law—Israel—and reminds us from Galatians that the Law was added because of sin; it did not take sin away but showed people their sin.