As distasteful as this is all rules and courtesy's should be applied equally to everyone or it is just the same as what many myself included complain about today with justice for some instead of justice for all being the order of the day.
My understanding is that all things "unclean" are deemed so for their foraging habits and their digestive structure, i.e. what they eat and how they process it seems to make the difference.
It is also my understanding that Paul brought to light our true libertarian nature, while advocating the personal voice of conscience in the matter.
Romans 14:14 - I know, and am persuaded by the Lord Jesus, that [there is] nothing unclean of itself: but to him that esteemeth any thing to be unclean, to him [it is] unclean.
A little research indicates why, even today, some delicacies are still best avoided, for health reasons, which is why I believe they were to be avoided "then". I find the admonitions in Scripture to be largely very practical when the origins and reasoning is looked into.