One popular argument used to support the eating of unclean meats is in Matthew 15:11.
Jesus said, "Not that which goeth into the mouth defileth a man; but that which cometh out of the mouth, this defileth a man."
Without consideration of the context, this verse seems to be saying that we may eat anything without being condemned or contaminated. But when we examine the entire chapter, we find that it has nothing to do with diet. From verse 2, we learn that Jesus was dealing with a controversy by the Pharisees, who insisted that the disciples give their hands a ceremonial washing before they ate food. The purpose of this bath was to cleanse away the defilement of touching any Gentile person or object.
Afterward, Peter asked Jesus, "Declare unto us this parable." Matthew 15:15. This statement proves that Christ's words were not to be taken literally, because a parable is merely a story or statement to illustrate a point. Notice how Jesus explained the meaning of His figurative statement: "Do not ye yet understand, that whatsoever entereth in at the mouth goeth into the belly, and is cast out into the draught? But those things which proceed out of the mouth come forth from the heart; and they defile the man. For out of the heart proceed evil thoughts, murders, adulteries, fornications, thefts, false witness, blasphemies: These are the things which defile a man: but to eat with unwashen handswith unwashen hands defileth not a man." Verses 17-20.
Now the whole story begins to clear up. Jesus knew that these religious leaders had murder in their hearts against Him, and yet their greatest concern was not over those evil dispositions, but only for a foolish tradition based on prejudice. That was the meaning of His parable. It did not refer to eating food, but rather to ceremonial washing.