So I turn them off as well in clouds.
I was IMC, deep in cloud There was this red light mind thumping ef'ing irritating distracting light show going on outside. I turned off the collision beacon. The F/O said, "are we allow to do that?" " We are now!" There then followed a lengthy discussion about the merits of using common sense. We decided that the rotating red beacon served naff all in preventing a collision; it was causing us no end of distraction, and merited turning off. The realisation from F/O that such deviation from SOP's was possible was astounding; and disturbing.
We survived to fly another day.