The Captain has the authority to do whenever he wants in an emergency, including deviating from any SOPīs he deems necessary to ensure the safety of the aircraft and its passengers. Period.
I hate this being used as an excuse for sloppy adherence to SOP.
For one to apply this rule and deviate from a major SOP the alternative consequence has to be utterly dire and I think too many pilots these days use it as an excuse to be sloppy.
In 15 years of flying airliners I have never come across an occasion where I have needed to deviate from SOP. There have been a few occasions in the Simulator but the alternative was the aeroplane burning up in flight.
BTW I like to think that I still manage to engender a relaxed atmosphere on the FD.