I truly believe that some listener's brains can't discern the difference sonic outputs from different pieces of equipment, cables, power conditioning, etc. Some of us can tell differences in the sonic signatures of various components. And of those of us who can tell sonic differences there is a range of being able to discern these differences.
I don't for a new York millisecond begrudge those listeners whose ears don't resolve differences in equipment. In turn, those who can't resolve sonic differences between audio kit need to quit harassing those of us who can.