You can check it out here:
His strategy was to do ad hominem without staying on point with the topic of the debate. "What is the best foundation for objective universal moral values and duties?".
The debate is NOT about if people of certain religions are more moral or not. It's a philosophical question. Communism killed about 100 million people in the 20th century and they've made religion illegal. That doesn't mean that all atheist are not capable of moral action. Saying that some religious people of the past were not moral is beside the point.
Basically, Sam Harris was coached to not engage at all. He attacked theism as the source of all evil, didn't defend the points of contention and didn't even try to bring a valid attack against how William was philosophically or logically wrong.
I was an atheist when I first saw this video and even thou I started with being on the side of Sam, I had to admit that if you look at it honestly, William destroyed the thesis of his book.
PS: and he never once tried to give an answer afterward on the attacks on his book.
Yeah, that sounds like the commentary on Quora about the debate as well.