So far we don't understand why Bitcoiners say, “Never sell your Bitcoin?” Your post doesn't explain anything.
I might be wrong here but I think that by "never sell your bitcoin," BitGoba meant that we shouldn't sell bitcoin as we usually do it for fiat, which is the inferior form of money, and from that point it doesn't make sense to exchange superior money for the inferior one.
Also, "never sell your bitcoin" doesn't mean that we shouldn't pay with bitcoin for the things we need.