As far as I'm concerned, SOPs are our servants, not our masters.
People also seem to think that safety is an absolute - i.e. that as flight (or an SOP) is either safe or it isn't, when in fact we are operating down at the end of the bell curve of unlikely events.
Our procedures just shift things slightly towards more safety (if they are well designed and implemented), without unduly compromising expediency.
No SOP can cover every situation. GPWS is just like every other warning system - a trade of between being sensitive enough to generate warnings when you need them versus not being over sensitive to the extent of providing too many false warnings.
I've had several GPWS warnings in my career, coincidentally they have all been in VMC. Solid VMC - i.e. 30 miles vis, rather than marginal, and not once have they been necessary. Fortunately, my employers at the time had SOP that allowed you to not pull up if you were in VMC and certain of position.
The fact is that there are many airfields where GPWS alerts are a fact of life. If you know the field you can turn to your colleague and say - 'The GPWS will probably go off right...now'.
Now don't get me wrong - if in anything less than solid VMC I'd be working on the automatic assumption that we had screwed up, and pull up / go around.
My new employers have the mandatory Pull up when below MSA. So next time I'm flying down to Jersey, and its a nice summers day without a cloud in the sky, and I join right base for 27 and the GPWS goes off as we fly over the cliffs, I'll be monstering back up to 3,000'. Will that be safer? - not one jot.
CPB