This was a somewhat formal debate (and informal beard-off) between two young Canadian men, both familiar with the basics of philosophy and theology, but not experienced in the art of public communication.
Michael Sizer-Watt debated Mariano Grinbank not on whether any gods really exist, but on whether one can make more sense of morality by grounding it in the assumptions of either naturalism or theism. They both have a go at the question, but ultimately they both miss the mark because neither addresses the key question "Why be moral" within the framework of his own worldview. Had they done so, they might have realized that they are both talking about acting in the interest of fulfilling one's own values, but operating on very different assumptions about the nature of reality under which one might go about doing so.
Sizer-Watt starts off with a concession that it is harder to establish what is right and wrong in a naturalist paradigm than it is to simply say "Morality is doing what X says" where X is a deity or a set of deities to whom we defer. He wants to argue for an alternative theory of ethics. He then goes on to describe the results of contemporary research at the boundaries of ethics and neuroscience. This is truly fascinating stuff, but it doesn't really prove anything about the nature of morality withoout throwing in several unspoken premises, such as "If morality has characteristics X, Y, Z, then it is
Grinbank, for his part, defines morality in terms of obedience to God and goes on to argue that it can only exist if God is there to obey. Not very convincing to the truly fence-sitting agnostic.
My advice is to skip this one, unless you really dig old man beards on young men.