Calm down about all this professionalism, CD, 2SO crews, max FTL rostering etc.
We are run (not led) by accountants.
When they do the cost benefit analysis on these events, they factor in an increased rate of diversion and recovery activity.
The accountants expect, and have budgeted for, a predicted number of diversions/recoveries. If you divert and decide to fight on through fatigue and/or use CD then all you are doing is taking ALL of the risk so that the account will end up under budget and trigger a bigger bonus!
If you call it a day after your rostered and planned duty, that included a diversion, then you are just operating to budget and as expected by the accountants.