I believe in unsanitary food, not "unclean" food. The rules may have made sense once upon a time: people get sick eating undercooked pork, don't eat pork; shellfish spoil much more easily than fin fish, don't eat shellfish; people that eat a lot of meat and dairy get fat and unhealthy, don't eat meat and dairy at the same time. Now we know the reasons for the bad things that can happen. I think they've out lived their usefulness.