1. If you have a light wave in the universe, and you "hang" a mass by each valley and trough of the light wave, and then you squash and stretch the universe, the masses stay connected to the valleys and troughs of the light wave. Said another way, when you squash and stretch space, lightwaves within that spacetime are also squashed and stretched.
2. LIGO claims to work by measuring the squashing and stretching space with light. However, as we just learned, squashing space also squashes light waves. So the LIGO arms and light waves in the arms are all compressed together.
Said another way, LIGO can't work because the ruler itself is squashing as space squashes, so you can't measure if space is compressing.
LIGO does work, but if you can't explain how it works despite this description, then you don't understand LIGO.