A light source emits equidistant pulses and an observer starts moving towards the source with speed v:
https://www.youtube.com/watch?v=bg7O4rtlwEE
The frequency at the moving observer shifts from f=c/d (frequency at the stationary observer) to f'=(c+v)/d, where d is the distance between subsequent pulses. Both relativists and antirelativists accept the formula f'=(c+v)/d. Sometimes the former speak of relativistic corrections (time dilation) but agree that, if v is small, the relativistic corrections can be ignored.
Given the formula f'=(c+v)/d, there are only two possibilities concerning the speed of light and the distance between subsequent pulses:
(1) Relative to the moving observer, the speed of light shifts from c to c'=c+v. That is, we have
f' = c'/d = (c+v)/d
The above formula is universally valid - whenever frequency and speed are considered, they vary proportionally. But the formula is clearly fatal for Einstein's special relativity.
(2) The motion of the observer somehow shifts the distance between the pulses from d to d'=dc/(c+v), so that the speed of light relative to the moving observer can gloriously remain unchanged. This is just as obviously idiotic as Big Brother's 2+2=5.
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