The deductive argument again:

Postulate 1: If the top of a tower of height h emits light with frequency f (as measured by the emitter), an observer on the ground will measure the frequency to be f'=f(1+gh/c^2) (confirmed by the Pound-Rebka experiment).

Postulate 2: There is gravitational time dilation as proposed by Einstein in 1911.

Postulate 3: The wavelength decreases as the light falls - if it is λ at the top of the tower, it will be λ'=λ/(1+gh/c^2) at the bottom.

Conclusion validly following from the postulates: The acceleration of the falling light is negative, -2g (that is, the speed of the light decreases as it falls). Yet the observer on the ground will measure the speed of the light to be c (unchanged).

This can loosely be described in the following way. In order for the Pound-Rebka experiment to be compatible with gravitational time dilation, the speed of light falling towards the source of gravity must DECREASE (the acceleration of falling photons must be NEGATIVE).

Clever Einsteinians know how idiotic the speed-of-falling-light-decreases prediction of Einstein's relativity is and either ignore it or mention it without any enthusiasm, as does John Norton at 13:14 he

https://www.youtube.com/watch?v=jc-QqYCSzF4
John Norton: Einstein's Discovery of the General Theory of Relativity

Pentcho Valev