Some may claim Acts 10 is an analogy (and it is), but it still applies both ways because of the deeper meaning. The entire purpose of clean vs unclean diets in the Old Testament was for the Jews to set an example to the world that there is a difference between the holy and the profane. Now that Christ has fulfilled the law and prophets, they are summed up as follows:
Therefore all things whatsoever ye would that men should do to you, do ye even so to them: for this is the law and the prophets.
-Mat 7:12
Or in other words, love your neighbor as yourself. Does your choice in meat affect your neighbor? Well, that depends.
If that meat is offered unto idols, and you eat of it willingly, it might cause them offense, and if they are offended, they may not hear the doctrine of Christ from you. Under that circumstance, Paul went a step further and said:
Wherefore, if meat make my brother to offend, I will eat no flesh while the world standeth, lest I make my brother to offend.
-1Co 8:13
This is the core understanding of loving your neighbor as yourself, and that love is selfless sacrifice. However, if that meat does not cause them offense, then he said:
All things are lawful for me, but all things are not expedient: all things are lawful for me, but all things edify not.
-1Co 10:23
(Expedient means "good for the purpose at hand;" Edify means to build up unto that which is righteous)
All things are lawful in the context of what is not sin. This is not to say that fornication is lawful by any means, but if we approach fornication from "thou shalt not commit adultery," then we have NOT understood the fullness of the law. If we approach fornication from a standpoint that God created all men and women, and they were designed to belong to one another in marriage, then we ought not to take away that which belongs to another (i.e. fornication is a form of theft), and when we consider others over ourselves, we love our neighbor as ourselves. (The same would apply to pornography, as abstaining from it is to be loving [give a selfless sacrifice] towards God, since the body is not our own [see Scripture below], but the temple of the Holy Ghost.)
Therefore, the fullness of the law is not "thou shalt not eat certain meats," but rather to question: How can I love my neighbor as myself? If I were preaching to the Jews, I likely would not eat pork among them for their sakes, that they might be willing to hear my doctrine, that Christ might bring them to repentance. If we think and live according to the fulfillment of the law and prophets, then we do not need to follow dietary laws; rather, we should follow the conviction of the Holy Spirit in every instance that we might love God and our neighbor as much (or more) than we love ourselves.
Thus:
All things are lawful unto me, but all things are not expedient: all things are lawful for me, but I will not be brought under the power of any. Meats for the belly, and the belly for meats: but God shall destroy both it and them. Now the body is not for fornication, but for the Lord; and the Lord for the body.
-1Co 6:12-13
