[huddles next to brianman in the nitpicker's corner]
Interestingly, no. According to the exceedingly well-researched UK Phrase Finder, "to take a statement with 'a grain of salt' or 'a pinch of salt' means to accept it but to maintain a degree of skepticism about its truth." Hence, a "large grain of salt" would correctly imply a large degree of skepticism.I thought the point of the grain of salt reference was that it should be considered inconsequential.