Is "their" mind the correct question ?
IF the SIC told the PIC: "no", then it was his mind.
Not sure if:
Duties of the Co-pilot
The operator had defined the duties of a co-pilot in the Operation Manual Part A, Chapter Organisation and Responsibilities, Chapter 1 of 27.03.2017. The following is an excerpt:
In-flight the Copilot shall:
[...] Inform the CMD11 automatically and immediately if something in the operation of the aeroplane is considered to become abnormal or if deviation from prescribed procedures, clearances or from the plan of operations showing up. [...]
is sufficient, when the CMD does something that stupid.