Do cable have an influence on the physical signal transfer (voltage/current/frequency)? Yes. Can this have an effect on the data signal transfer? In certain situations it might. Does this matter for the sound quality of digital audio/video signals? No.
A digital data distribution either works or it works not (works as in "the receiving end gets the data the sender send out"). There is no ambiguity like in analog signals. Bad cable may lead to the loss of data but that would only result in gaps/skipping in your audio (or video) playback and not in any kind of quality difference in the analog audio data that is decoded from the digital data.
(Graph is for HDMI<->Picture but the principal is the same for USB<->Audio)
(Source: http://reviews.cnet.com/8301-33199_7-57540275-221/still-more-reasons-why-all-hdmi-cable-are-the-same/ )
I won't even start to argue with you on this. You obviously have your believes set straight and I don't argue on believes of any any kind. If you ever want to change your mind though the links provided by atomik are a really good read.