How do you argue with a finite universe creationist?

Try pointing out that if space were to actually relativistically expand, the speed of light would also have to increase, in order to remain CONSTANT!

When two metrics are being derived from the same light, one based on speed and the other based on spectrum, it's simply an issue of which is numerator and which is denominator.

If the speed were the numerator, it would be a "tired light" theory, but since the premise is an, "expanding space" theory, the speed is still the explicit denominator. The ruler against which this expansion is measured.

Suffice to say, it will take a preponderance of evidence to crack that nut, not mere logic, given how invested the field has become in its current version of epicycles/patches over the many gaps. Inflation, Dark Matter, Dark Energy.