First of all, that we are "in the Matrix" is one of a zillion zillion functionally equivalent and indistinguishable theories of "simulated reality". While we're at it, maybe we're in the Matrix1 in the Matrix2. Maybe in the Matrix3. Maybe in the Matrix4. Etc.

So your friend is just incorrect. Once you admit "The Matrix" as a possibility, you're committed to admitting an infinite number of theories into your universe of discussion, so the odds of The Matrix being true are 1 out of infinity.

Bur as long as we're not contesting the statistical regularities we observe where ever we are, I don't care which of the zillion we're in. Until your friend comes up with observable and falsifiable consequences to his Meta Reality, I will treat it as a superfluous complication to my model.

Until "we're in the Matrix" can pay rent, it's not living in my head.