I've lived in Labrador all my life, and we always kill a few seals a year. When we, and a lot of people in my province , use a gun to kill seals, and aim for the head. Sometimes my uncles or grandfather set seal nets to catch seals. From what I've seen, shot seals die quickly or instantly. The bodies are then pulled aboard the boat or komatik (a sled towed by dogs or snowmobile) with the head over the gunnel to let the blood drain. When we arrive in town or return to the cabin, the (dead! They'd be to wild to skin alive!) seal is skinned and cleaned. Sometimes the intestines are cleaned out and dried, and the skin scraped of fat and stretched on wooden frames to be dried and sold.
Yes, seal meat eating and trading is acceptable, because it is similar to other meats. Eating seal meat is no more inhumane than eating other types of mammals, or of eating fish. If a business wants to raise seals simply for the purpose of harvesting them for meat, it should be considered no different from running a dairy farm. Controls should be put in place to make sure this is done in a humane way.
It might be a way of life to eat the meat of the seals and if indigenous people must survive on their meat, then that is a different story, but the brutal and horrific ways in which seals are slaughtered make it hard for me to justify people selling their meat for profit.