Except that it's not over the max FDP. The max FDP that you're talking about is the planned FDP, but the science recognizes that people are frequently able to exceed those limits without issue, and the rule therefore allows you to do it if you aren't fatigued. If you aren't fatigued, why do you think you should be able to deny the assignment anyway? Because if it's not a safety issue, then it's a contract issue. Address it through the right venue, which isn't a regulation.
So what is the reason for the max FDP to be published in the reg then? Why not just publish the max FDP as the FDP+2 hours?
The FAA is being naive the think that the "employer-employee" relationship at the regional level is anything but hostile. Adding to that the FAA is naive in thinking that regional management would not take full advantage of this interpretation to build schedules they shouldn't be allowed to.
My company consistently build pairings within 15-30 minutes of max FDP with the full knowledge that they can just force the pilots to extend it anyway.