Hey Chiterne flyer.....loved reading your post. This is a major issue with carriers that dont have well developed sched rules.
I have at times in the past been face with exactly the same conflict. I was hauled onto the red carpet a couple of times for the exact same reason. Not for getting upset at the scheduler, but for plain refusing to operate the flight. I just told them to find someone else...I was fatigued and a safety risk to fly. They wanted to put a letter in my file too. I refused to sign the letter there, and I said I had a right to fill in the rest of the details. When I did, and brought it back again with the entire story, they didn't like it. Haha...because you know what, it implicated the company and not me. I was told I have a bad attitude!! How's that! What...they want me to fall asleep while landing??? The stupidity is shocking at times and really frustrating.
Anyway, maybe you could recommend to your union to push some better sched rules. One model that works that I've seen is an "A" and "B" reserve. A is for first half of the day, B for the second. Company has to give you 24 hours notice to change your reserve time. Flight must commence in the 12 hour period, and limited to a certian length. That ensures coverage, and fair treatment to the Pilot. Just think what the passengers would think if they knew what your company was pulling. And shame on the management for saying it was your fault....obviously not a very mature managment attitude.
Cheers.