Recent letters concerning shark fin have shown unquestioning acceptance of a dogma.
There is a refusal on the part of correspondents to consider opposing viewpoints when dealing with those they consider to be the unenlightened.
Joan Miyaoka's letter ("Tuna being wiped out through greed", January 8) sees the diversity of the oceans crumbling, because the greedy "educated and wealthy" do not share her view that Chinese people should refuse to eat sharks and tuna.
Self-proclaimed "thinking people" such as Laurence Mead ("Time to stop defending the indefensible", January 11) see seafood drying on rooftops as akin to cage homes for the elderly - his logic, not mine - with no place in civilised society.
Outside of their views lies the uncivilised "la-la land" in which people are unaware that the amount of food required to feed today's human population is more than it was 150 years ago. This is a profound insight. Their mantra is not new. The [early Christian] author Tertullian said that "we weigh upon the world; its resources hardly suffice to support us. As our needs grow larger, so do our protests that already nature does not sustain us". But nature has sustained us, and with rational management will continue to do so.
Biodiversity losses in the oceans are trivial relative to those that have occurred in the swamps, rivers, forests and savannahs degraded for centuries to feed, clothe and shelter people.