In a debate with David Wood over the source of morality, Matt Dillahunty effectively admitted that, in his worldview, morality is not objective. Rather, it is a set of rules that boost the survival chances of a society that enforces them. The irony of the debate is that David Wood is a psychopath. This is not an insult, this is a genuine medical problem he has. As a psychopath, David Wood has no natural desire or inclination to obey moral rules imposed by society. And so a simple question for Matt, who lost the debate just by even entering it with a literal psychopath, would be why should a person, like Dr. Wood, obey these rules?
One of the silliest answers he gave was that we should all obey these rules because we have already benefited from them. There are several problems with this, including the fact that it doesn't establish an obligation to follow these beneficial systems. But the bigger flaw is that what is beneficial and what is moral are two different things. There are benefits to some very evil acts. For example, a lot of medical advancements came out of Nazi Germany, not through ethical experimentation, but by some horrible atrocities committed against Jews.
Now, as both a sinner, and a notorious blasphemer, Matt obviously has quite the spiritual rap sheet. We all do. But I would be somewhat surprised if I saw him openly sympathising with the Nazis. So, once again, Matt's argument disintegrates, leaving him with the unfortunate task of trying to justify morality without God. This, of course, can never be done. Without God, a moral commandment becomes a creative suggestion. Good becomes "things I like", and evil becomes "things I don't like". Effectively, when a man does not acknowledge God, that man becomes his own god. It is easy to sit on a throne you believe is unoccupied.
But when that throne is occupied, this is called "treason". Or, as the Bible calls it, "sin". Each and every one of us has rebelled against God, and just as treason against a human government typically carries the death penalty, so also does sin result in death. But God is a special kind of ruler. He is not only perfect in His justice, but also perfect in His love. Love even for His enemies. Therefore, though death is called for, death is not desirable. So what did God do? Crucified Jesus. Jesus Christ, the Son of God, became a man, lived a perfect life, and died the death you should have received. Then He rose again. If you repent, confess Him as Lord, and believe He rose, you will be saved. That's something you've benefited from, and so by Matt Dillahunty's logic, you must obey it.