The guest argues that if you want to be a strict physicalist, then you are forced into the many-worlds interpretation, with infinitely many copies of you.
Normally I would say that he is using bad Physics to justify his spiritual beliefs, but there are many respected atheist physicists who say the same thing.
I may be in the minority, but I say that strict physicalism means just believing in what is physically observable, and that rules out many-worlds. Believing in unobservable parallel universes and many copies of yourself is just another spiritual/religious belief, about like believing in the Bible. Believe in it if you want, but do not pretend that it is scientific, or logical, or strictly physical. It is not.