Call crew control and tell them you are too fatigued to do the flight. That easy, next. Oh, sticking you head above the parapet thingy is it.
Don’t write an ASR/MOR as that will stick your head well above the parapet. Maybe a CHIRP, yes that’s it a CHIRP. A CHIRP gets filed to the GMA and does absolutely nothing about it. CAD has no idea it is happening.
If you don’t write an ASR/MOR nothing will be done. If you don’t want to write an ASR/MOR, don’t complain.

Do you realize that anyone can write an ASR/MOR i.e. First and Second Officers included?
Of course you may be called and intimidated not to send it in as an MOR, but decline the offer, send it in.

Next!